Influence of Electric Field and Carrier Localization on Carrier Dynamics in AlGaN Quantum Wells

Dynamics of nonequilibrium carriers in high-Al-content AlGaN/AlGaN multiple quantum wells was studied. A set of multiple quantum wells with well widths varying from 1.65 to 5.0 nm was grown by metal-organic chemical vapor deposition. The structures were investigated by photoluminescence spectroscopy under quasi-steady-state conditions. The observed blueshift of the photoluminescence band peak was attributed to the screening of the built-in electric field. The integrated photoluminescence intensity dependence on excitation and temperature showed a strong influence of carrier localization

Influence of Electric Field and Carrier Localization on Carrier Dynamics in AlGaN Quantum Wells

Dynamics of nonequilibrium carriers in high-Al-content AlGaN/AlGaN multiple quantum wells was studied. A set of multiple quantum wells with well widths varying from 1.65 to 5.0 nm was grown by metal-organic chemical vapor deposition. The structures were investigated by photoluminescence spectroscopy under quasi-steady-state conditions. The observed blueshift of the photoluminescence band peak was attributed to the screening of the built-in electric field. The integrated photoluminescence intensity dependence on excitation and temperature showed a strong influence of carrier localization

Luminescence of Highly Excited Nonpolar a-Plane GaN and AlGaN/GaN Multiple Quantum Wells

Carrier recombination dynamics in polar and nonpolar GaN epilayers and GaN/AlGaN multiple quantum wells grown over sapphire substrates with various crystallographic orientation were studied under high photoexcitation by 20 ps laser pulses. The transient of luminescence featured a significant enhancement in nonradiative recombination of free carriers for nonpolar a-plane GaN epilayers compared to conventional c-plane samples. The epitaxial lateral overgrowth technique was demonstrated to significantly improve the quality of nonpolar a-plane films. This was proved by more than 40-fold increase in luminescence decay time (430 ps compared to ≤10 ps in the ordinary a-plane epilayer). Under high-excitation regime, a complete screening of built-in electric field by free carriers in multiple quantum wells grown on c-plane and r-plane sapphire substrates was achieved. Under such high excitation, luminescence efficiency and carrier lifetime of multiple quantum wells was shown to be determined by the substrate quality

Luminescence of Highly Photoexcited GaN Epilayers and Heterostructures Grown on Different Sapphire Crystal Planes

GaN epilayers and AlGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition on different crystal planes (c, a, and r) of the sapphire substrate were studied by excitation intensity dependent and time-resolved photoluminescence. In polar multiple quantum wells grown on a- and c-planes, a blueshift of the luminescence band with increasing the excitation energy was observed, indicating that screening of built-in field by free carriers takes place, whereas in nonpolar r-plane grown multiple quantum wells, the luminescence band maintained an almost constant peak position. Full screening of built-in field was achieved at the excitation densities higher than 0.3 mJ/cm$\text{}^{2}$. Under conditions of screened built-in electric field the structures were characterized by carrier lifetime. It was shown that nonpolar multiple quantum wells suffer from high density of nonradiative traps that can be due to substrate related threading dislocations

Luminescence of Highly Photoexcited GaN Epilayers and Heterostructures Grown on Different Sapphire Crystal Planes

GaN epilayers and AlGaN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition on different crystal planes (c, a, and r) of the sapphire substrate were studied by excitation intensity dependent and time-resolved photoluminescence. In polar multiple quantum wells grown on a- and c-planes, a blueshift of the luminescence band with increasing the excitation energy was observed, indicating that screening of built-in field by free carriers takes place, whereas in nonpolar r-plane grown multiple quantum wells, the luminescence band maintained an almost constant peak position. Full screening of built-in field was achieved at the excitation densities higher than 0.3 mJ/cm$\text{}^{2}$. Under conditions of screened built-in electric field the structures were characterized by carrier lifetime. It was shown that nonpolar multiple quantum wells suffer from high density of nonradiative traps that can be due to substrate related threading dislocations

Suppression of Defect-Related Luminescence in Laserannealed InGaN Epilayers

An In 0.21Ga 0.79N epilayer has been studied by using spatially-resolved photoluminescence spectroscopy and Auger electron spectroscopy. The photoluminescence intensity is shown to be distributed highly inhomogeneously, while the epilayer also exhibits strong defect-related emission. It is shown that laser annealing at high enough power densities causes redistribution of indium atoms and results in suppression of the defect-related emission. ? 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim