Emission studies of InGaN layers and LEDs grown by plasma-assisted MBE

We prepared InGaN layers on GaN/sapphire substrates using rf-MBE. Photolumi nescence (PL) from these layers, grown at different temperatures Ts, shows that there is a strong tendency of GaN to form a separate phase as Ts is in creased from 600 degreesC to 650 degreesC. Concomitant with the phase separ ation, the PL from the InGaN phase broadens, which indicates that indium co mposition in this phase becomes increasingly non-uniform. Indium compositio ns measured by Rutherford backscattering (RBS) are consistent with these re sults. We also observed an increase in PL intensity for InGaN layers grown at higher temperatures. In this paper, we also report on preparing a top-co ntact InGaN/GaN light emitting diode. The device was operated at 447 run an d had the emission line width of 37 nm with no observable impurity related features. The turn-on voltage was 3.0 V. The output power was 20 muW at 60 mA drive current. (C) 2001 Elsevier Science B.V. All rights reserved.