Photoluminescence Studies of Polarization Effects in InGaN/(In)GaN Multiple Quantum Well Structures

The impact of polarization fields in multiple quantum well (MQW) structures is revealed by photoluminescence measurements and band diagram calculations. We observe a blue shift of luminous energy of 33 meV and an increased light emission of 19% for In x Ga1-x N/In y Ga1-y N MQWs with respect to In x Ga1-x N/GaN MQWs. Band diagram calculations show a lowering of the polarization fields and an increase in wave function overlap of 22% by adding indium into the barriers. We therefore attribute the observed blue shift and increased emission to an improved electron and hole wave function overlap due to lower electric fields in In x Ga1-x N/In y Ga1-y N structures.