Influence of indium composition in the prestrained InGaN interlayer on the strain relaxation of InGaN/GaN multiple quantum wells in laser diode structures

Prestrained InGaN layers with different indium composition were grown by metalorganic chemical vapor deposition as an interlayer before the growth of InGaN/GaN multiple quantum wells (MQWs) in laser diode structures. The strain relaxation of the MQWs with different indium composition prestrained InGaN interlayer was investigated by the grazing incidence x-ray diffraction method. Comparing to the low indium composition (about 3%) case, the strain relaxation occurred in the sample with high indium composition (about 10%) prestrained interlayer. The piezoelectric field in the MQW is also proved to be much smaller after inserting a high indium composition prestrained InGaN interlayer by a measurement of photoluminescence (PL) peak shift as a function of reverse bias voltage, indicating a reduction of the quantum-confined Stark effect (QCSE). Room temperature PL and temperature-dependent PL measurements showed that the PL intensity at 300 K and the internal quantum efficiency of the MQW sample with high indium composition prestrained interlayer were increased by 123% and 177%, respectively, compared with the low indium composition case. Therefore, the prestrained InGaN interlayer containing high indium composition is beneficial to the strain relaxation in the MQW layer and the enhancement of light emission efficiency due to the reduction of QCSE.