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

S. Juršėnasa, S. Miasojedovasa, G. Kurilčika, V. Liuoliaa, A. Žukauskasa, C.Q. Chenb, J.W. Yangb, E. Kuokštisb, V. Adivarahanb and M. Asif Khanb aInstitute of Materials Science and Applied Research, Vilnius University, Sauletekio 9-III, 10222 Vilnius, Lithuania bDepartment of Electrical Engineering, University of South Carolina, Columbia, SC 29208, USA

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Received: 22 08 2004;

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/cm2. 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.

DOI: 10.12693/APhysPolA.107.235 PACS numbers:78.55.Cr, 73.21.Fg, 72.20.Jv, 78.47.+p