AFM image of (a) indium rich InGaN QDs deposited on the InGaN wetting layer, (b) single QW sample B with clusters of InGaN QDs formed by layer growth of the InGaN well layer which wets the QDs, (c) single QW sample C with stripelike AlN islands on the InGaN well formed with addition of AlN capped layer, (d) second QDs layer with higher density grown on single QWs sample C, (e) sample B with annealing at for 10 min, and (f) sample C with annealing at for 10 min.
HR-STEM image taken along direction for (a) sample B with embedded InGaN QDs in the InGaN well layers, (b) sample B after thermal annealing which illustrated the out-diffusion of QDs to the surrounding matrix and interdiffusion into the GaN barrier causing the shrinkage of the QDs dimension, and (c) sample C after thermal annealing with the QDs better preserved but with some out-diffusion into the InGaN active well region.
PL spectra at 10 K for (a) sample C and (b) sample B before and after thermal annealing for 10 min in ambient.
Current dependent EL spectra for (a) LEDs X and (b) LEDs Y with chamber annealing for 20 min in ambient at for Mg activation. (c) Plot of the light-output power and peak emission wavelength of LEDs as a function of injection current.
Schematic representation of the energy band profile of strained AlN/InGaN QDs/InGaN/GaN QW system.
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