Determination of carrier concentration and quantum efficiency in InGaN/GaN quantum wells using photomodulated reflectivity (Conference Presentation)

We present a combined photoluminescence (PL) and photomodulated reflectivity (PMR) study of three GaN/InGaN multiquantum well samples. We reported previously that the change in carrier concentration (n) induced by the pump beam can be measured by lock-in techniques using a simple Drude model to calculate n from the change in reflectivity. Here we extend the work by simultansously measuring a thermal signal from the sample, we can thus measure the internal quantum efficiency ηi of samples as a function of carrier concentration. This yields an ηi vs n curve that is strikingly different to those reported previously by PL and electroluminescent techniques (EL), with a very rapid (in n) drop off due to the droop process.