Kendall Dawkins | North Carolina Agricultural and Technical State University (original) (raw)
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Papers by Kendall Dawkins
Nanotechnology, Jul 9, 2024
Nanotechnology, Apr 18, 2023
In this work, we present a systematic design of growth experiments and subsequent characterizatio... more In this work, we present a systematic design of growth experiments and subsequent characterization of self-catalyzed molecular beam epitaxially grown GaAsSb heterostructure axial p–i–n nanowires (NWs) on p-Si <111> for the ensemble photodetector (PD) application in the near-infrared region. Diverse growth methods have been explored to gain a better insight into mitigating several growth challenges by systematically studying their impact on the NW electrical and optical properties to realize a high-quality p–i–n heterostructure. The successful growth approaches are Te-dopant compensation to suppress the p-type nature of intrinsic GaAsSb segment, growth interruption for strain relaxation at the interface, decreased substrate temperature to enhance supersaturation and minimize the reservoir effect, higher bandgap compositions of the n-segment of the heterostructure relative to the intrinsic region for boosting the absorption, and the high-temperature ultra-high vacuum in situ annealing to reduce the parasitic radial overgrowth. The efficacy of these methods is supported by enhanced photoluminescence (PL) emission, suppressed dark current in the heterostructure p–i–n NWs accompanied by increased rectification ratio, photosensitivity, and a reduced low-frequency noise level. The PD fabricated utilizing the optimized GaAsSb axial p–i–n NWs exhibited the longer wavelength cutoff at ∼1.1 μm with a significantly higher responsivity of ∼120 A W−1 (@−3 V bias) and a detectivity of 1.1 × 1013 Jones operating at room temperature. Frequency and the bias independent capacitance in the pico-Farad (pF) range and substantially lower noise level at the reverse biased condition, show the prospects of p–i–n GaAsSb NWs PD for high-speed optoelectronic applications.
ACS applied electronic materials, Aug 27, 2020
Bandgap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE) ... more Bandgap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE) and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in the near-infrared region is reported. Stringent control on NW nucleation conditions, stem growth duration, and NW exposure to the N-plasma were found to be critical for the successful growth of high-quality dilute nitride quaternary GaAsSbN NW in the axial configuration. Planar defect-free structures were realized with room temperature photoluminescence (PL) characteristics, revealing reduced N-induced point defects and non-radiative recombination centers. N incorporation in the dilute nitride NWs was ascertained from PL and Raman spectral mode shifts and shapes and weak temperature-dependent PL peak energy. The advantage of Te-doping in dilute nitride NW using a GaTe captive source is the compensation of point defects is demonstrated, as evidenced by a significant improvement in PL characteristics, Raman mode shifts, and spectral shape with improved photodetector device performance relative to intrinsic dilute nitride NWs. Te-doped GaAsSbN NW Schottky based photodetectors have been demonstrated on both single and ensemble configurations with a resultant responsivity of 5 A/W at 860 nm and 3800 A/W at 1100, respectively. Detectivity of 3.2x10 10 Jones was achieved on the Te-doped ensemble NW device. The findings presented in this work showcase prospects for rich bandgap engineering using doped GaAsSbN NW for near-infrared-region device applications.
Nanotechnology, Jul 26, 2022
Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanos... more Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. Recently, it was found that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz (THz) probe spectroscopy (OPTP) and electrical characterization have been used to study non-equilibrium carrier dynamics and equilibrium transport in Te-doped GaAsSb and dilute nitride GaAsSb NWs, with the goal of correlating these results with their photo-response under bias and their low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering rate, resulting in a severe reduction in carrier mobility. Carrier recombination lifetimes of 33 ± 1 ps and 147 ± 3 ps in GaAsSbN and GaAsSb NWs, respectively, were determined using ultrafast OPTP measurements. The reduction in the carrier lifetime and photoinduced optical conductivities are due to the presence of Ninduced defects, leading to deterioration in the electrical and optical characteristics of dilute nitride NWs relative to the non-nitride NWs. Finally, we observed a very fast rise time of ~ 2 ps for both NW materials, directly impacting their potential use as high-speed photodetectors.
ACS applied nano materials, Mar 20, 2023
Nanoscale advances, 2022
In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate ... more In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (V BR) of $ À10 AE 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at V BR at a 1.064 mm wavelength. Positive temperature dependence of breakdown voltage $ 12.6 mV K À1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance-voltage (C-V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I-V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cutoff wavelength of 1.2mmwitharesponsivityof1.2 mm with a responsivity of 1.2mmwitharesponsivityof0.17-0.38 A W À1 at À3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.
Nanotechnology, Mar 9, 2023
ACS Applied Nano Materials
Nanoscale Advances
In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate ... more In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented.
Crystal Growth & Design
Nanotechnology
This work evaluates the passivation efficacy of thermal atomic layer deposited (ALD) Al2O3 dielec... more This work evaluates the passivation efficacy of thermal atomic layer deposited (ALD) Al2O3 dielectric layer on self-catalyzed GaAs1-x Sb x nanowires (NWs) grown using molecular beam epitaxy. A detailed assessment of surface chemical composition and optical properties of Al2O3 passivated NWs with and without prior sulfur treatment were studied and compared to as-grown samples using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature photoluminescence (PL) spectroscopy. The XPS measurements reveal that prior sulfur treatment followed by Al2O3 ALD deposition abates III–V native oxides from the NW surface. However, the degradation in 4K-PL intensity by an order of magnitude observed for NWs with Al2O3 shell layer compared to the as-grown NWs, irrespective of prior sulfur treatment, suggests the formation of defect states at the NW/dielectric interface contributing to non-radiative recombination centers. This is corroborated by the Raman spectral broadening of...
ACS Applied Electronic Materials
Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and d... more Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in th...
Nanotechnology
Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanos... more Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. Recently, it was found that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz probe spectroscopy has been used to study non-equilibrium carrier dynamics and transport in Te-doped GaAsSb and dilute nitride GaAsSbN NWs, with the goal of correlating these results with electrical characterization of their equilibrium photo-response under bias and low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering...
Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and d... more Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in th...
Nanotechnology, Jul 9, 2024
Nanotechnology, Apr 18, 2023
In this work, we present a systematic design of growth experiments and subsequent characterizatio... more In this work, we present a systematic design of growth experiments and subsequent characterization of self-catalyzed molecular beam epitaxially grown GaAsSb heterostructure axial p–i–n nanowires (NWs) on p-Si <111> for the ensemble photodetector (PD) application in the near-infrared region. Diverse growth methods have been explored to gain a better insight into mitigating several growth challenges by systematically studying their impact on the NW electrical and optical properties to realize a high-quality p–i–n heterostructure. The successful growth approaches are Te-dopant compensation to suppress the p-type nature of intrinsic GaAsSb segment, growth interruption for strain relaxation at the interface, decreased substrate temperature to enhance supersaturation and minimize the reservoir effect, higher bandgap compositions of the n-segment of the heterostructure relative to the intrinsic region for boosting the absorption, and the high-temperature ultra-high vacuum in situ annealing to reduce the parasitic radial overgrowth. The efficacy of these methods is supported by enhanced photoluminescence (PL) emission, suppressed dark current in the heterostructure p–i–n NWs accompanied by increased rectification ratio, photosensitivity, and a reduced low-frequency noise level. The PD fabricated utilizing the optimized GaAsSb axial p–i–n NWs exhibited the longer wavelength cutoff at ∼1.1 μm with a significantly higher responsivity of ∼120 A W−1 (@−3 V bias) and a detectivity of 1.1 × 1013 Jones operating at room temperature. Frequency and the bias independent capacitance in the pico-Farad (pF) range and substantially lower noise level at the reverse biased condition, show the prospects of p–i–n GaAsSb NWs PD for high-speed optoelectronic applications.
ACS applied electronic materials, Aug 27, 2020
Bandgap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE) ... more Bandgap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy (MBE) and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in the near-infrared region is reported. Stringent control on NW nucleation conditions, stem growth duration, and NW exposure to the N-plasma were found to be critical for the successful growth of high-quality dilute nitride quaternary GaAsSbN NW in the axial configuration. Planar defect-free structures were realized with room temperature photoluminescence (PL) characteristics, revealing reduced N-induced point defects and non-radiative recombination centers. N incorporation in the dilute nitride NWs was ascertained from PL and Raman spectral mode shifts and shapes and weak temperature-dependent PL peak energy. The advantage of Te-doping in dilute nitride NW using a GaTe captive source is the compensation of point defects is demonstrated, as evidenced by a significant improvement in PL characteristics, Raman mode shifts, and spectral shape with improved photodetector device performance relative to intrinsic dilute nitride NWs. Te-doped GaAsSbN NW Schottky based photodetectors have been demonstrated on both single and ensemble configurations with a resultant responsivity of 5 A/W at 860 nm and 3800 A/W at 1100, respectively. Detectivity of 3.2x10 10 Jones was achieved on the Te-doped ensemble NW device. The findings presented in this work showcase prospects for rich bandgap engineering using doped GaAsSbN NW for near-infrared-region device applications.
Nanotechnology, Jul 26, 2022
Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanos... more Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. Recently, it was found that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz (THz) probe spectroscopy (OPTP) and electrical characterization have been used to study non-equilibrium carrier dynamics and equilibrium transport in Te-doped GaAsSb and dilute nitride GaAsSb NWs, with the goal of correlating these results with their photo-response under bias and their low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering rate, resulting in a severe reduction in carrier mobility. Carrier recombination lifetimes of 33 ± 1 ps and 147 ± 3 ps in GaAsSbN and GaAsSb NWs, respectively, were determined using ultrafast OPTP measurements. The reduction in the carrier lifetime and photoinduced optical conductivities are due to the presence of Ninduced defects, leading to deterioration in the electrical and optical characteristics of dilute nitride NWs relative to the non-nitride NWs. Finally, we observed a very fast rise time of ~ 2 ps for both NW materials, directly impacting their potential use as high-speed photodetectors.
ACS applied nano materials, Mar 20, 2023
Nanoscale advances, 2022
In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate ... more In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented. Our device exhibits a low breakdown voltage (V BR) of $ À10 AE 2.5 V under dark, photocurrent gain (M) varying from 20 in linear mode to avalanche gain of 700 at V BR at a 1.064 mm wavelength. Positive temperature dependence of breakdown voltage $ 12.6 mV K À1 further affirms avalanche breakdown as the gain mechanism in our SACM NW APDs. Capacitance-voltage (C-V) and temperature-dependent noise characteristics also validated punch-through voltage ascertained from I-V measurements, and avalanche being the dominant gain mechanism in the APDs. The ensemble SACM NW APD device demonstrated a broad spectral room temperature response with a cutoff wavelength of 1.2mmwitharesponsivityof1.2 mm with a responsivity of 1.2mmwitharesponsivityof0.17-0.38 A W À1 at À3 V. This work offers a potential pathway toward realizing tunable nanowire-based avalanche photodetectors compatible with traditional Si technology.
Nanotechnology, Mar 9, 2023
ACS Applied Nano Materials
Nanoscale Advances
In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate ... more In this study, molecular beam epitaxially grown axially configured ensemble GaAsSb/GaAs separate absorption, charge, and multiplication (SACM) region-based nanowire avalanche photodetector device on non-patterned Si substrate is presented.
Crystal Growth & Design
Nanotechnology
This work evaluates the passivation efficacy of thermal atomic layer deposited (ALD) Al2O3 dielec... more This work evaluates the passivation efficacy of thermal atomic layer deposited (ALD) Al2O3 dielectric layer on self-catalyzed GaAs1-x Sb x nanowires (NWs) grown using molecular beam epitaxy. A detailed assessment of surface chemical composition and optical properties of Al2O3 passivated NWs with and without prior sulfur treatment were studied and compared to as-grown samples using x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature photoluminescence (PL) spectroscopy. The XPS measurements reveal that prior sulfur treatment followed by Al2O3 ALD deposition abates III–V native oxides from the NW surface. However, the degradation in 4K-PL intensity by an order of magnitude observed for NWs with Al2O3 shell layer compared to the as-grown NWs, irrespective of prior sulfur treatment, suggests the formation of defect states at the NW/dielectric interface contributing to non-radiative recombination centers. This is corroborated by the Raman spectral broadening of...
ACS Applied Electronic Materials
Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and d... more Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in th...
Nanotechnology
Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanos... more Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. Recently, it was found that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz probe spectroscopy has been used to study non-equilibrium carrier dynamics and transport in Te-doped GaAsSb and dilute nitride GaAsSbN NWs, with the goal of correlating these results with electrical characterization of their equilibrium photo-response under bias and low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering...
Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and d... more Band gap engineering of GaAsSbN nanowires (NWs) grown by Ga-assisted molecular beam epitaxy and demonstration of a Te-doped axial GaAsSbN NW-based Schottky barrier photodetector on p-Si (111) in th...