Optical-pumping spectra for In_xGa_1-xN/GaN multiple quantum well structures with indium content x>0.35

Photoluminescence (PL) measurement and optical pumping at 25 K were studied for high-indium-composition InGaN/GaN multiple quantum well (MQW) structures grown by low-pressure metalorganic chemical vapor deposition. The result show that thermal annealing can reduce the compositional fluctuation of indium content. The optical pumping spectra show 5 stimulated emission (SE) peaks. This phenomenon might be attributed to intersubband transition. The transition between quantized levels for each peak was precisely identified by solving the time-independent Schrodinger equation and finite-difference method. The ratio of conduction-band discontinuities to valence-band discontinuities of InGaN/GaN QW, ΔE_C:ΔE_V = 38:62, can be obtained.