Introduction

Spectral photoluminescence (PL) is a non-contact, non-destructive, spectroscopy-based measurement technique to probe the electronic structure of different materials. Spectral PL can be used to obtain information on the emission properties of different heterostructures (quality control) and/or crystal structure of the material. Photoluminescence is a photon emission process that occurs during relaxation from electronic and/or localized (defects) excited states. Charge carriers can recombine through Shockley-Read-Hall (SRH) and radiative recombination simultaneously. The radiative recombination rate is proportional with the product of electron and hole concentrations. As the minority carrier density is decreased by the SRH recombination that takes place at defects and impurities, the radiative recombination is inversely proportional to defect density and impurity concentration. During radiative recombination, a photon is emitted, which can be detected by a spectrograph. This is the photoluminescence (PL) signal.