Absolute evaluation of internal and external quantum efficiencies and light extraction efficiency in InGaN single quantum wells by simultaneous photoacoustic and photoluminescence measurements combined with integrating-sphere method

Separated evaluation of factors in the external quantum efficiency (EQE) is important in order to improve the characteristics of semiconductors optical devices. Especially, the internal quantum efficiency (IQE) is an important value which indicates crystal quality of the active layers, and an accurate method for estimating the IQE values is required. The IQE is usually estimated from temperature dependence of photoluminescence (PL) intensity by assuming that the IQE at cryogenic temperature is 100%. However, III-nitride semiconductor materials, used in many optical devices, usually have large defect density, and the assumption is not necessarily valid. In our previous report, we demonstrated the simultaneous photoacoustic (PA) and PL measurements to accurately estimate the IQE values in GaN films with various qualities and obtained reasonable results. In this work, we have successfully realized reproducible measurements with high accuracy for an InGaN-QW sample by suppressing the background noise significantly. Furthermore, we have also measured the values of EQE by using an integrating-sphere. Since the light extraction efficiency (LEE) can be obtained by the values of IQE and EQE, it has been shown that the overall picture of emission efficiency can be provided by our method.