Absolute Measurement of Emission Internal Quantum Efficiency in III-Nitride Semiconductors by Simultaneous PhotoAcoustic and Photoluminescence Spectroscopy

Abstract

Emission internal quantum efficiency (IQE) is an important index evaluating the quality of active layers in optical devices. The IQE is usually estimated from temperature dependence of photoluminescence (PL) intensity by assuming that the IQE at cryogenic temperature is 100 %. III-nitride films, however, usually have high-density crystal defects, and it cannot be said that the assumption is valid. In 2016, we proposed a new method to estimate accurate IQE values by simultaneous PL and photo-acoustic (PA) measurements, and demonstratively evaluated the IQE values for various GaN samples. After that, we applied the method to InGaN quantum-well active layers and estimated the IQE values and their excitation carrier-density dependence in the layers. In this paper, we will introduce the principle of our simultaneous PA/PL measurement and will present some examples of absolute measurement of IQE values in III-nitride semiconductor samples.