Photoluminescence-linewidth-derived reduced exciton mass for In_ {y} Ga_ {1-y} As_ {1-x} N_ {x} alloys (original) (raw)
Related papers
2009
InGaN based, blue and green light emitting diodes (LEDs) have been successfully produced over the past decade. But the progress of these LEDs is often limited by the fundamental problems of InGaN such as differences in lattice constants, thermal expansion coefficients and physical properties between InN and GaN. This difficulty could be addressed by studying pure InN and In x Ga 1-x N alloys. In this context Ga-rich In x Ga 1-x N (x≤ 0.4) epilayers were grown by metal organic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) measurements showed In x Ga 1-x N films with x= 0.37 had single phase. Phase separation occurred for x ~ 0.4. To understand the issue of phase separation in Ga-rich In x Ga 1-x N, studies on growth of pure InN and In-rich In x Ga 1-x N alloys were carried out. InN and In-rich In x Ga 1-x N (x~0.97-0.40) epilayers were grown on AlN/Al 2 O 3 templates. A Hall mobility of 1400 cm 2 /Vs with a carrier concentration of 7x10 18 cm-3 was observed for InN epilayers grown on AlN templates. Photoluminescence (PL) emission spectra revealed a band to band emission peak at ~0.75 eV for InN. This peak shifted to 1.15 eV when In content was varied from 1.0 to 0.63 in In-rich In x Ga 1-x N epilayers. After growth parameter optimization of In-rich In x Ga 1-x N alloys with (x= 0.97-0.40) were successfully grown without phase separation. Effects of Mg doping on the PL properties of InN epilayers grown on GaN/Al 2 O 3 templates were investigated. An emission line at ~ 0.76 eV, which was absent in undoped InN epilayers and was about 60 meV below the band edge emission peak at ~ 0.82 eV, was observed to be the dominant emission in Mg-doped InN epilayers. PL peak position and the temperature dependent emission intensity corroborated each other and suggested that Mg acceptor level in InN is about 60 meV above the valance band maximum. Strain effects on the emission properties of InGaN/GaN multiple quantum wells (MQWs) were studied using a single blue LED wafer possessing a continuous variation in compressive strain. EL emission peak position of LEDs varies linearly with the biaxial strain; a coefficient of 19 meV/GPa, characterizes the relationship between the band gap energy and biaxial stress of In 0.2 Ga 0.8 N/GaN MQWs.
Advanced Engineering Materials, 2002
Semiconductor heterostructures based on different compositions of the same alloy are important for the realization of new electronic and photonic devices. Stepped quantum wells are considered as good candidates for the enhancement of non-linear optical properties. There have been, however, very few studies devoted to the properties of the alloy±alloy interface common to all these materials. Previous investigations on the optical properties of In-GaAs±GaAs strained symmetric quantum wells (SQW) have provided considerable evidence on the high quality achievable in samples grown with this type of semiconductor alloy material. [3±5] On the contrary, we observe that while stepped± asymmetric quantum well (AQW) reflectivity (R) spectra agree well with theory, photoluminescence (PL) spectra show a somewhat peculiar behavior. In this study we concentrate on the power and temporal dependence of the AQW PL to illustrate a phenomenology consistent with exciton localization at the alloy±alloy interface.
Opto-Electronics Review, 2009
We have investigated optical properties of Ga 0.64 In 0. 36 N 0.006 As 0.994 /GaAs single quantum−well structures using photo− luminescence technique. We have found that nitrogen creates potential fluctuations in the InGaNAs structures, so it is the cause of trap centres in these structures and leads to localized excitons recombination dynamics. The near−band edge PL at 2 K exhibited a blueshift with an increase in excitation intensity of a sample but there is not such a shift in the PL peak position energy of same sample at 150 K. It has been found that PL spectra have a large full width at half maximum (FWHM) value at 2 K. These results are discussed in terms of carrier localization. Additionally, our results suggest decreasing PL integrated intensity in this structure, possibly due to non−radiative recombination. It has been shown that thermal annealing reduces the local strain created by nitrogen. By annealing process, a blue shifted emission can be observed.
Spectral distribution of excitation-dependent recombination rate in an In0. 13Ga0. 87N epilayer
Generalized model of the dielectric function of AlInGaP alloys J. Appl. Phys. 113, 093103 (2013) Correlations between the morphology and emission properties of trench defects in InGaN/GaN quantum wells J. Appl. Phys. 113, 073505 (2013) Optical characterization of free electron concentration in heteroepitaxial InN layers using Fourier transform infrared spectroscopy and a 2×2 transfer-matrix algebra J. Appl. Phys. 113, 073502 (2013) Influence of structural anisotropy to anisotropic electron mobility in a-plane InN Appl. Phys. Lett. 102, 061904 (2013) Temperature dependent carrier dynamics in telecommunication band InAs quantum dots and dashes grown on InP substrates
Small band gap bowing in In1−xGaxN alloys
Applied Physics Letters, 2002
High-quality wurtzite-structured In-rich In 1-x Ga x N films (0 ≤ x ≤ 0.5) have been grown on sapphire substrates by molecular-beam epitaxy. Their optical properties were characterized by optical absorption and photoluminescence spectroscopy. The investigation reveals that the narrow fundamental bandgap for InN is near 0.8eV and that the bandgap increases with increasing Ga content. Combined with previously reported results on the Ga-rich side, the bandgap versus composition plot for In 1-x Ga x N alloys is well fit with a bowing parameter of ~ 1.4 eV. The direct bandgap of the In 1-x Ga x N system covers a very broad spectral region ranging from near-infrared to near-ultraviolet.
Band Gap of Hexagonal InN and InGaN Alloys
physica status solidi (b), 2002
A survey of most recent studies of optical absorption, photoluminescence, photoluminescence excitation, and photomodulated reflectance spectra of single-crystalline hexagonal InN layers is presented. The samples studied were undoped n-type InN with electron concentrations between 6 Â 10 18 and 4 Â 10 19 cm --3 . It has been found that hexagonal InN is a narrow-gap semiconductor with a band gap of about 0.7 eV, which is much lower than the band gap cited in the literature. We also describe optical investigations of In-rich In x Ga 1--x N alloy layers (0.36 < x < 1) which have shown that the bowing parameter of b $ 2.5 eV allows one to reconcile our results and the literature data for the band gap of In x Ga 1--x N alloys over the entire composition region. Special attention is paid to the effects of post-growth treatment of InN crystals. It is shown that annealing in vacuum leads to a decrease in electron concentration and considerable homogenization of the optical characteristics of InN samples. At the same time, annealing in an oxygen atmosphere leads to formation of optically transparent alloys of InN-In 2 O 3 type, the band gap of which reaches approximately 2 eV at an oxygen concentration of about 20%. It is evident from photoluminescence spectra that the samples saturated partially by oxygen still contain fragments of InN of mesoscopic size.
The ternary semiconductor GaAs 1-x N x with 0 < x < 0.3 can be grown epitaxially on GaAs and has a very large bowing coefficient. The alloy bandgap can be reduced to about 1.0 eV with about a 3% nitrogen addition. In this work, we measured the internal spectral response and recombination lifetime of a number of alloys using the ultra-high frequency photoconductive decay (UHFPCD) method. The data shows that the photoconductive excitation spectra of the GaAs 0.97 N 0.03 alloy shows a gradual increase in response through the absorption edge near E g. This contrasts with most direct bandgap semiconductors that show a steep onset of photoresponse at E g. The recombination lifetimes frequently are much longer than expected from radiative recombination and often exceeded 1.0 µs. The data was analyzed in terms of a band model that includes large potential fluctuations in the conduction band due to the random distribution of nitrogen atoms in the alloy. photovoltaics ; double heterostructures ; recombination lifetimes ; ultra-high frequency photoconductive decay 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified