Transient and quasi-steady-state photoluminescence of a dense electron-hole plasma was studied in GaN epilayers under high photoexcitation at room-temperature. High initial carrier heating up to 1100 K was observed. Decay of nonthermalized electron-hole plasma was analyzed both in homo- and heteroepitaxial GaN layers. The heating is shown to significantly influence the luminescence peak position and the rate of spontaneous and stimulated recombination. After the thermalization process is completed, the luminescence decay is exponential and the room-temperature carrier lifetime can be extracted. The lifetime in the heteroepitaxial layer grown on sapphire was found to be 190 ps, while the homoepitaxial layer exhibited an essentially higher value of 890 ps, which is one of the highest reported for free-carrier recombination in GaN. Additionally, optical gain spectra were studied using variable-stripe method. The threshold for stimulated emission was found to be considerably lower and the gain at a certain pump intensity was shown to be much higher in the homoepitaxial layer than in the heteroepitaxial one. Maximum net gain value of 300 cm^-1 was observed.

Date Published: 8 March 2001
PDF: 6 pages
Proc. SPIE 4318, Smart Optical Inorganic Structures and Devices, (8 March 2001); doi: 10.1117/12.417587

Published in SPIE Proceedings Vol. 4318:
Smart Optical Inorganic Structures and Devices
Steponas P. Asmontas; Jonas Gradauskas, Editor(s)