E. Armour - Academia.edu (original) (raw)
Papers by E. Armour
Conference Proceedings. 1997 International Conference on Indium Phosphide and Related Materials, 1997
ABSTRACT Two sets of In0.5(Ga1-xAlx)0.5P/GaAs were prepared by metalorganic chemical vapor deposi... more ABSTRACT Two sets of In0.5(Ga1-xAlx)0.5P/GaAs were prepared by metalorganic chemical vapor deposition, and a combined photoluminescence (PL) and Raman scattering investigation was performed. Variations of PL bands and Raman lines were observed from one set of samples with x~24% and grown with different pressures and dopants. Both the PL and Raman measurements confirmed the Al-compositional variations of the second set of samples, with x~18% and grown under different low pressures and H2 flows, to be around 1%. It is found that the Raman spectral features are more sensitive to the epitaxial growth parameter variations. The line shape analysis leads to information about the sample crystalline quality and the optimum growth conditions, which is coincident with the qualitative analysis of the growth process. This study offers us a useful way to optimize the parameters to produce high crystalline quaternary InGaAlP materials
2000 IEEE International Symposium on Compound Semiconductors. Proceedings of the IEEE Twenty-Seventh International Symposium on Compound Semiconductors (Cat. No.00TH8498), 2000
ABSTRACT Using surface photovoltage spectroscopy (SPS) and contactless electroreflectance (CER) {... more ABSTRACT Using surface photovoltage spectroscopy (SPS) and contactless electroreflectance (CER) {including [110] and [11¯0] polarizations} we have characterized the emitter (CER), collector (CER), and base (SPS) of a GaInP/GaAs (001) heterojunction bipolar transistor, fabricated by metalorganic chemical vapor deposition. CER yields information about the emitter (including ordering) and collector, but produces no signal from the heavily p-doped base. However, SPS has been used to evaluate the minority carrier transport properties and related common-emitter gain factor (β) in this section. The SPS spectrum is a function of both the absorption coefficient and minority carrier transport properties in the relevant portions of the sample. The SPS data indicates 190<β<290
ECS Transactions, 2013
ABSTRACT Confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) spe... more ABSTRACT Confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) spectroscopy were used to study blue-emitting indium gallium nitride (InGaN)/gallium nitride (GaN) multi-quantum wells grown on c-plane sapphire substrate by metal-organic chemical vapor deposition under different growth conditions. Spatial and spectral variations of photoluminescence (PL) were observed in sub-micrometer scale. Spectrum measurement showed that the bright regions have higher PL intensity as well as smaller PL peak energy than the dark regions. The brightness of CLSM images is related with the PL peak energy difference between bright region and dark region: the larger the energy difference is, the brighter the CLSM image is. TRPL measurement and calculation showed that the effective PL lifetime at bright regions is longer than that at dark regions, and brightness of CLSM images increases with the increment of bright region effective PL lifetime.
MRS Proceedings, 2001
ABSTRACT This paper addresses issues with the manufacturability of AlGaN/GaN FET structures. A ro... more ABSTRACT This paper addresses issues with the manufacturability of AlGaN/GaN FET structures. A robust Metalorganic Chemical Vapor Deposition growth process has been developed that will now allow reliability measurements to be obtained on the resulting devices. During a small scale production run mobilities in excess of 1600 cm2/V.s, sheet charge (Ns) between 0.8x1013 and 1.2x1013 cm-2, and Rs<400 Ω/square with less than 2% variation across the wafer and less than 0.5% variation from wafer to wafer were obtained. Issues for producing a manufacturable process on sapphire and semi-insulating SiC substrates using in-situ monitoring will be addressed. The equivalence of growth on sapphire and SiC substrates for process optimization will be shown.
Device Research Conference. Conference Digest (Cat. No.01TH8561), 2001
Solid-State Electronics, 2002
ABSTRACT A current gain β of 23 is demonstrated from a small-area NpN GaAs-based double heterojun... more ABSTRACT A current gain β of 23 is demonstrated from a small-area NpN GaAs-based double heterojunction bipolar transistor (HBT) using a low band-gap InGaAsN material (lattice matched to GaAs with an energy band gap EG of 1.2 eV) as the base layer. An improved band-gap engineering design at both emitter–base and base–collector heterojunctions in this GaAs-based HBT structure allows significant turn-on voltage reduction up to 270 mV compared to conventional InGaP/GaAs HBTs, while attaining high-speed performance. Self-aligned devices with emitter active area of 3×5 μm2 show cutoff frequency fT and maximum oscillation frequency fMAX values of 32 and 52 GHz, respectively. These results demonstrate the strong potential of this novel HBT technology to reduce power consumption in future wireless handsets using the GaAs manufacturing platform.
We report the fabrication of double heterojunction bipolar transistors (DHBTs) with the use of a ... more We report the fabrication of double heterojunction bipolar transistors (DHBTs) with the use of a new quaternary InGaAsN material system that takes advantage of a low energy band gap in the base to reduce operating voltages in GaAs-based electronic devices. InGaP/In0.03Ga0.97As0.99N0.01 /GaAs DHBTs with improved band gap engineering at both heterojunctions exhibit a DC peak current gain over 16 with small active emitter area. The use of the InGaAsN base layer allows a significant reduction of the turn-on voltage by 250 mV for the new technology over a standard InGaP/GaAs HBT, while maintaining high-frequency characteristics with cut-off frequency and maximum oscillation frequency as high as 40 GHz and 70 GHz, respectively. This technology is promising for next generation RF circuits using GaAs-based HBTs by reducing the operating voltage for low power consumption and better handling of supply voltages in advanced wireless handsets
physica status solidi (a), 2003
Metal-organic chemical vapor deposition (MOCVD) epitaxial layers (n-GaN, InGaN/GaN multiple quant... more Metal-organic chemical vapor deposition (MOCVD) epitaxial layers (n-GaN, InGaN/GaN multiple quantum well (MQW) and p-GaN) of GaN based green light emitting diodes (LEDs) structures have been sequentially grown on c-plane sapphire substrate with slight misorientation from the c plane. The qualities of these sequentially grown epitaxial layers show a strong dependence of the misorientation. Structural and optical characterization demonstrate the
Journal of Crystal Growth, 2011
Increasing demand for high brightness LEDs for LCD TV backlighting and solid-state lighting requi... more Increasing demand for high brightness LEDs for LCD TV backlighting and solid-state lighting requires MOCVD growth of GaN at high growth rates (4 5 mm/h) with high crystalline quality in mass production reactors. Understanding the MOCVD growth parameters on the quality of GaN materials and growth efficiency are important for quickly setting up process windows for the optimization and qualification of new LED growth processes. We have investigated the effects of N 2 /H 2 ratio, N 2 /NH 3 ratio, and growth temperature on the growth efficiency, crystal quality, morphology, yellow-band emission (YE), and sheet resistance of un-doped GaN epitaxial layers using design of experiment (DOE) methodology. Our results indicate that high growth temperature (at 1080 1C) and low N 2 /H 2 ratio (set at 0.5 in the DOE) were the common factors for achieving better crystal quality, smoother surface, and lower YE intensity in GaN epitaxial layers, as well as for obtaining higher growth efficiency in MOCVD of GaN.
Journal of Crystal Growth, 2006
The effect of temperature and excitation power on the characteristics of InGaN/GaN single quantum... more The effect of temperature and excitation power on the characteristics of InGaN/GaN single quantum well (SQW) and multiple quantum well (MQW) light-emitting diodes (LED) has been investigated in-depth over a broad range of temperatures from 9 to 300 K. It was found that the device with a stair-shaped SQW structure exhibited stronger localization effect, as well as had higher internal quantum efficiency than that of the conventional MQW and SQW LEDs. This is interpreted as due to the stair-shaped SQW configuration, which offered a large contribution to the exciton capturing. The adoption of an appropriate heterostructure in active region allows the achievement of improved LED performance. With increasing the excitation power intensity, QW photoluminescence (PL) line broadening and emission peak blue shifts were observed, which are assumed to be caused by the disordering formed in the Inrich heterostructures of QW ensembles. We expect that distinct degree of carrier localization occurs in these samples. r
Journal of Crystal Growth, 1997
ABSTRACT As more compound semiconductor devices reach large volume manufacturing levels, a trend ... more ABSTRACT As more compound semiconductor devices reach large volume manufacturing levels, a trend toward the use of the MOVPE technique is clear. In this paper we examine the criteria needed for MOVPE equipment suitable for large scale manufacturing. We find that although uniformity and device performance are necessary, reproducibility is also critical, along with high throughput and low operating costs. These points are illustrated by actual examples including MMIC power amplifiers, HB-LEDs, and solar cells. A realistic COO model provides a tool for evaluating MOVPE systems of different capacities. In situ control of key parameters during growth is now feasible, and will become an important method for increasing reproducibility and throughput. Lastly we look at the prospects for automation, for decreasing labor costs as well as wafer handling. This is likely to first have an impact on systems for the growth of electronic device structures on large (100 and 150 mm) wafers.
[sub 0.52]P films grown on GaAs (001) by low pressure metalorganic chemical vapor deposition](https://attachments.academia-assets.com/41725373/thumbnails/1.jpg)
](Journal of Applied Physics, 1999
The quaternary alloy In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P, lattice-matched to GaAs, has a direct band ga... more The quaternary alloy In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P, lattice-matched to GaAs, has a direct band gap transition in the wavelength range of green-red light and is useful in optoelectronic applications such as visible light emitting diodes and laser diodes. We have investigated a set of six nominal In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P layers that were grown on GaAs ͑001͒ by low pressure metalorganic chemical vapor deposition ͑MOCVD͒ turbo disk technology. In order to control and optimize the growth conditions to produce high quality InGaAlP epilayers, a variety of nondestructive techniques, including photoluminescence ͑PL͒, Raman scattering, photoreflectance ͑PR͒, reflectance anisotropy ͑RA͒ spectroscopy, atomic force microscopy ͑AFM͒, and high resolution x-ray diffraction ͑HRXRD͒ have been applied to evaluate the epitaxial films and growth processes. HRXRD confirmed a good lattice match between the epilayers and the substrate material. The PL and PR spectra showed the variations of the InGaAlP PL peak and the energy band with growth pressure and other parameters. Raman spectral line shape analysis leads to information about the sample crystalline quality. Polarization dependent PR and RA spectroscopy were used to detect the in-plane anisotropy of epitaxial materials. AFM was used to study the surface morphology of these quaternary compounds and to nondestructively detect any possible dislocations in these hetero-epitaxial materials. The optimized parameters for the growth of high quality InGaAlP films on GaAs were obtained. The combination of these nondestructive techniques offers a better understanding of MOCVD-grown In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P/GaAs and a useful way to optimize the growth parameters of high quality quaternary semiconductor materials.
IEEE Photonics Technology Letters, 2000
Inverting optical logic gates based on the monolithic integration of a vertical-cavity surface-em... more Inverting optical logic gates based on the monolithic integration of a vertical-cavity surface-emitting laser (VCSEL) with a heterojunction photothyristor (PNPN) are dementally demonstrated for the first time using latchable and cascadable PNPNPCSEL switches, which can be triggered with very low optical energy, while producing high-optical gain and optical contrast. These gates are integrable on a single epitaxial structure to provide multifunctional logic and memory arrays. scribed. LO& fUIICtiOnS INVERT, NAND, and NOR are experi-ERTICAL-CAVITY surface-emitting laser (VCSEL)-V based optical switches and optical logic gates [I]-[4]
IEEE Photonics Technology Letters, 2000
GaAs/AIGaAs vertical-cavity top-surface-emitting lasers with a continuously graded mirror composi... more GaAs/AIGaAs vertical-cavity top-surface-emitting lasers with a continuously graded mirror composition have been grown by MOCVD, and planar devices with proton-implant current confinement have been characterized. Continuous grading of the heterointerfaces in the Bragg reflectors eliminated the energy-band discontinuities, thus improving carrier transport and resulting in a substantial reduction in the series resistance and threshold voltage of the laser diodes. These VCSEL's have excellent room-temperature CW electrical characteristics, including some of the lowest series resistance, highest power efficiency, and lowest operating voltages ever reported.
IEEE Photonics Technology Letters, 2000
We report the first demonstration of a cascadable photonic switch based on the monolithic integra... more We report the first demonstration of a cascadable photonic switch based on the monolithic integration of a multiquantum-well vertical-cavity surface-emitting laser (VCSEL) and a latching pn-pn photothyristor grown by LP-MOCVD. The VCSEL and pn-pn photothyristor structures can be independently optimized for optical switching, logic and memory functions. Optical switching with high gain (30 OOO), high contrast (30 dB), low switching power (11 nW), and latching memory have been demonstrated.
Applied Physics Letters, 2002
The incorporation of a low band gap carbon-doped InGaAsN material into a standard GaAs heterojunc... more The incorporation of a low band gap carbon-doped InGaAsN material into a standard GaAs heterojunction bipolar transistor (HBT) has great potential to achieve higher operating efficiency at lower bias conditions. In order to improve the performance of the initial as-grown InGaAsN-based HBTs (with 1% N and 3% In for an energy band gap EG of 1.2 eV), the effects of
Applied Physics Letters, 2014
We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InG... more We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above $5 Â 10 18 cm À3 , a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses. V C 2014 AIP Publishing LLC. [http://dx.
Conference Proceedings. 1997 International Conference on Indium Phosphide and Related Materials, 1997
ABSTRACT Two sets of In0.5(Ga1-xAlx)0.5P/GaAs were prepared by metalorganic chemical vapor deposi... more ABSTRACT Two sets of In0.5(Ga1-xAlx)0.5P/GaAs were prepared by metalorganic chemical vapor deposition, and a combined photoluminescence (PL) and Raman scattering investigation was performed. Variations of PL bands and Raman lines were observed from one set of samples with x~24% and grown with different pressures and dopants. Both the PL and Raman measurements confirmed the Al-compositional variations of the second set of samples, with x~18% and grown under different low pressures and H2 flows, to be around 1%. It is found that the Raman spectral features are more sensitive to the epitaxial growth parameter variations. The line shape analysis leads to information about the sample crystalline quality and the optimum growth conditions, which is coincident with the qualitative analysis of the growth process. This study offers us a useful way to optimize the parameters to produce high crystalline quaternary InGaAlP materials
2000 IEEE International Symposium on Compound Semiconductors. Proceedings of the IEEE Twenty-Seventh International Symposium on Compound Semiconductors (Cat. No.00TH8498), 2000
ABSTRACT Using surface photovoltage spectroscopy (SPS) and contactless electroreflectance (CER) {... more ABSTRACT Using surface photovoltage spectroscopy (SPS) and contactless electroreflectance (CER) {including [110] and [11¯0] polarizations} we have characterized the emitter (CER), collector (CER), and base (SPS) of a GaInP/GaAs (001) heterojunction bipolar transistor, fabricated by metalorganic chemical vapor deposition. CER yields information about the emitter (including ordering) and collector, but produces no signal from the heavily p-doped base. However, SPS has been used to evaluate the minority carrier transport properties and related common-emitter gain factor (β) in this section. The SPS spectrum is a function of both the absorption coefficient and minority carrier transport properties in the relevant portions of the sample. The SPS data indicates 190<β<290
ECS Transactions, 2013
ABSTRACT Confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) spe... more ABSTRACT Confocal laser scanning microscopy (CLSM) and time-resolved photoluminescence (TRPL) spectroscopy were used to study blue-emitting indium gallium nitride (InGaN)/gallium nitride (GaN) multi-quantum wells grown on c-plane sapphire substrate by metal-organic chemical vapor deposition under different growth conditions. Spatial and spectral variations of photoluminescence (PL) were observed in sub-micrometer scale. Spectrum measurement showed that the bright regions have higher PL intensity as well as smaller PL peak energy than the dark regions. The brightness of CLSM images is related with the PL peak energy difference between bright region and dark region: the larger the energy difference is, the brighter the CLSM image is. TRPL measurement and calculation showed that the effective PL lifetime at bright regions is longer than that at dark regions, and brightness of CLSM images increases with the increment of bright region effective PL lifetime.
MRS Proceedings, 2001
ABSTRACT This paper addresses issues with the manufacturability of AlGaN/GaN FET structures. A ro... more ABSTRACT This paper addresses issues with the manufacturability of AlGaN/GaN FET structures. A robust Metalorganic Chemical Vapor Deposition growth process has been developed that will now allow reliability measurements to be obtained on the resulting devices. During a small scale production run mobilities in excess of 1600 cm2/V.s, sheet charge (Ns) between 0.8x1013 and 1.2x1013 cm-2, and Rs<400 Ω/square with less than 2% variation across the wafer and less than 0.5% variation from wafer to wafer were obtained. Issues for producing a manufacturable process on sapphire and semi-insulating SiC substrates using in-situ monitoring will be addressed. The equivalence of growth on sapphire and SiC substrates for process optimization will be shown.
Device Research Conference. Conference Digest (Cat. No.01TH8561), 2001
Solid-State Electronics, 2002
ABSTRACT A current gain β of 23 is demonstrated from a small-area NpN GaAs-based double heterojun... more ABSTRACT A current gain β of 23 is demonstrated from a small-area NpN GaAs-based double heterojunction bipolar transistor (HBT) using a low band-gap InGaAsN material (lattice matched to GaAs with an energy band gap EG of 1.2 eV) as the base layer. An improved band-gap engineering design at both emitter–base and base–collector heterojunctions in this GaAs-based HBT structure allows significant turn-on voltage reduction up to 270 mV compared to conventional InGaP/GaAs HBTs, while attaining high-speed performance. Self-aligned devices with emitter active area of 3×5 μm2 show cutoff frequency fT and maximum oscillation frequency fMAX values of 32 and 52 GHz, respectively. These results demonstrate the strong potential of this novel HBT technology to reduce power consumption in future wireless handsets using the GaAs manufacturing platform.
We report the fabrication of double heterojunction bipolar transistors (DHBTs) with the use of a ... more We report the fabrication of double heterojunction bipolar transistors (DHBTs) with the use of a new quaternary InGaAsN material system that takes advantage of a low energy band gap in the base to reduce operating voltages in GaAs-based electronic devices. InGaP/In0.03Ga0.97As0.99N0.01 /GaAs DHBTs with improved band gap engineering at both heterojunctions exhibit a DC peak current gain over 16 with small active emitter area. The use of the InGaAsN base layer allows a significant reduction of the turn-on voltage by 250 mV for the new technology over a standard InGaP/GaAs HBT, while maintaining high-frequency characteristics with cut-off frequency and maximum oscillation frequency as high as 40 GHz and 70 GHz, respectively. This technology is promising for next generation RF circuits using GaAs-based HBTs by reducing the operating voltage for low power consumption and better handling of supply voltages in advanced wireless handsets
physica status solidi (a), 2003
Metal-organic chemical vapor deposition (MOCVD) epitaxial layers (n-GaN, InGaN/GaN multiple quant... more Metal-organic chemical vapor deposition (MOCVD) epitaxial layers (n-GaN, InGaN/GaN multiple quantum well (MQW) and p-GaN) of GaN based green light emitting diodes (LEDs) structures have been sequentially grown on c-plane sapphire substrate with slight misorientation from the c plane. The qualities of these sequentially grown epitaxial layers show a strong dependence of the misorientation. Structural and optical characterization demonstrate the
Journal of Crystal Growth, 2011
Increasing demand for high brightness LEDs for LCD TV backlighting and solid-state lighting requi... more Increasing demand for high brightness LEDs for LCD TV backlighting and solid-state lighting requires MOCVD growth of GaN at high growth rates (4 5 mm/h) with high crystalline quality in mass production reactors. Understanding the MOCVD growth parameters on the quality of GaN materials and growth efficiency are important for quickly setting up process windows for the optimization and qualification of new LED growth processes. We have investigated the effects of N 2 /H 2 ratio, N 2 /NH 3 ratio, and growth temperature on the growth efficiency, crystal quality, morphology, yellow-band emission (YE), and sheet resistance of un-doped GaN epitaxial layers using design of experiment (DOE) methodology. Our results indicate that high growth temperature (at 1080 1C) and low N 2 /H 2 ratio (set at 0.5 in the DOE) were the common factors for achieving better crystal quality, smoother surface, and lower YE intensity in GaN epitaxial layers, as well as for obtaining higher growth efficiency in MOCVD of GaN.
Journal of Crystal Growth, 2006
The effect of temperature and excitation power on the characteristics of InGaN/GaN single quantum... more The effect of temperature and excitation power on the characteristics of InGaN/GaN single quantum well (SQW) and multiple quantum well (MQW) light-emitting diodes (LED) has been investigated in-depth over a broad range of temperatures from 9 to 300 K. It was found that the device with a stair-shaped SQW structure exhibited stronger localization effect, as well as had higher internal quantum efficiency than that of the conventional MQW and SQW LEDs. This is interpreted as due to the stair-shaped SQW configuration, which offered a large contribution to the exciton capturing. The adoption of an appropriate heterostructure in active region allows the achievement of improved LED performance. With increasing the excitation power intensity, QW photoluminescence (PL) line broadening and emission peak blue shifts were observed, which are assumed to be caused by the disordering formed in the Inrich heterostructures of QW ensembles. We expect that distinct degree of carrier localization occurs in these samples. r
Journal of Crystal Growth, 1997
ABSTRACT As more compound semiconductor devices reach large volume manufacturing levels, a trend ... more ABSTRACT As more compound semiconductor devices reach large volume manufacturing levels, a trend toward the use of the MOVPE technique is clear. In this paper we examine the criteria needed for MOVPE equipment suitable for large scale manufacturing. We find that although uniformity and device performance are necessary, reproducibility is also critical, along with high throughput and low operating costs. These points are illustrated by actual examples including MMIC power amplifiers, HB-LEDs, and solar cells. A realistic COO model provides a tool for evaluating MOVPE systems of different capacities. In situ control of key parameters during growth is now feasible, and will become an important method for increasing reproducibility and throughput. Lastly we look at the prospects for automation, for decreasing labor costs as well as wafer handling. This is likely to first have an impact on systems for the growth of electronic device structures on large (100 and 150 mm) wafers.
Journal of Applied Physics, 1999
The quaternary alloy In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P, lattice-matched to GaAs, has a direct band ga... more The quaternary alloy In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P, lattice-matched to GaAs, has a direct band gap transition in the wavelength range of green-red light and is useful in optoelectronic applications such as visible light emitting diodes and laser diodes. We have investigated a set of six nominal In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P layers that were grown on GaAs ͑001͒ by low pressure metalorganic chemical vapor deposition ͑MOCVD͒ turbo disk technology. In order to control and optimize the growth conditions to produce high quality InGaAlP epilayers, a variety of nondestructive techniques, including photoluminescence ͑PL͒, Raman scattering, photoreflectance ͑PR͒, reflectance anisotropy ͑RA͒ spectroscopy, atomic force microscopy ͑AFM͒, and high resolution x-ray diffraction ͑HRXRD͒ have been applied to evaluate the epitaxial films and growth processes. HRXRD confirmed a good lattice match between the epilayers and the substrate material. The PL and PR spectra showed the variations of the InGaAlP PL peak and the energy band with growth pressure and other parameters. Raman spectral line shape analysis leads to information about the sample crystalline quality. Polarization dependent PR and RA spectroscopy were used to detect the in-plane anisotropy of epitaxial materials. AFM was used to study the surface morphology of these quaternary compounds and to nondestructively detect any possible dislocations in these hetero-epitaxial materials. The optimized parameters for the growth of high quality InGaAlP films on GaAs were obtained. The combination of these nondestructive techniques offers a better understanding of MOCVD-grown In 0.48 ͑Ga 1Ϫx Al x ) 0.52 P/GaAs and a useful way to optimize the growth parameters of high quality quaternary semiconductor materials.
IEEE Photonics Technology Letters, 2000
Inverting optical logic gates based on the monolithic integration of a vertical-cavity surface-em... more Inverting optical logic gates based on the monolithic integration of a vertical-cavity surface-emitting laser (VCSEL) with a heterojunction photothyristor (PNPN) are dementally demonstrated for the first time using latchable and cascadable PNPNPCSEL switches, which can be triggered with very low optical energy, while producing high-optical gain and optical contrast. These gates are integrable on a single epitaxial structure to provide multifunctional logic and memory arrays. scribed. LO& fUIICtiOnS INVERT, NAND, and NOR are experi-ERTICAL-CAVITY surface-emitting laser (VCSEL)-V based optical switches and optical logic gates [I]-[4]
IEEE Photonics Technology Letters, 2000
GaAs/AIGaAs vertical-cavity top-surface-emitting lasers with a continuously graded mirror composi... more GaAs/AIGaAs vertical-cavity top-surface-emitting lasers with a continuously graded mirror composition have been grown by MOCVD, and planar devices with proton-implant current confinement have been characterized. Continuous grading of the heterointerfaces in the Bragg reflectors eliminated the energy-band discontinuities, thus improving carrier transport and resulting in a substantial reduction in the series resistance and threshold voltage of the laser diodes. These VCSEL's have excellent room-temperature CW electrical characteristics, including some of the lowest series resistance, highest power efficiency, and lowest operating voltages ever reported.
IEEE Photonics Technology Letters, 2000
We report the first demonstration of a cascadable photonic switch based on the monolithic integra... more We report the first demonstration of a cascadable photonic switch based on the monolithic integration of a multiquantum-well vertical-cavity surface-emitting laser (VCSEL) and a latching pn-pn photothyristor grown by LP-MOCVD. The VCSEL and pn-pn photothyristor structures can be independently optimized for optical switching, logic and memory functions. Optical switching with high gain (30 OOO), high contrast (30 dB), low switching power (11 nW), and latching memory have been demonstrated.
Applied Physics Letters, 2002
The incorporation of a low band gap carbon-doped InGaAsN material into a standard GaAs heterojunc... more The incorporation of a low band gap carbon-doped InGaAsN material into a standard GaAs heterojunction bipolar transistor (HBT) has great potential to achieve higher operating efficiency at lower bias conditions. In order to improve the performance of the initial as-grown InGaAsN-based HBTs (with 1% N and 3% In for an energy band gap EG of 1.2 eV), the effects of
Applied Physics Letters, 2014
We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InG... more We report on diffusion-driven and excitation-dependent carrier recombination rate in multiple InGaN/GaN quantum wells by using photoluminescence, light-induced absorption, and diffraction techniques. We demonstrate gradually increasing with excitation carrier diffusivity and its correlation with the recombination rate. At low carrier densities, an increase in radiative emission and carrier lifetime was observed due to partial saturation of non-radiative recombination centers. However, at carrier densities above $5 Â 10 18 cm À3 , a typical value of photoluminescence efficiency droop, a further increase of diffusivity forces the delocalized carriers to face higher number of fast non-radiative recombination centers leading to an increase of non-radiative losses. V C 2014 AIP Publishing LLC. [http://dx.