Characterization of semiconductor crystals based on omnidirectional photoluminescence (ODPL) spectroscopy

Abstract

Omnidirectional photoluminescence (ODPL) spectroscopy, which can determine the internal quantum efficiency (IQE) of freestanding semiconductor crystals with direct bandgap without the need for model calculations, is reviewed. ODPL can determine IQE from the external quantum efficiency (EQE) based on the fact that light with self-absorption energy in the vicinity of the band-edge of a freestanding semiconductor crystal is emitted mainly in the normal direction of crystal surface. The procedure and applications of IQE determination are discussed using gallium nitride, zinc oxide, and metal halide perovskite as example cases. In particular, the ability to measure a large crystal sample outside an integrating sphere is one of the main features of ODPL spectroscopy, and it is expected to be combined with mapping measurements of the entire surface of semiconductor wafers and various types of nonlinear and microscopic spectroscopy.