Characterization of wide-gap semiconductors by photothermal deflection spectroscopy

Abstract

Abstract Group III–V nitride semiconductors have been characterized by photothermal deflection spectroscopy (PDS) which can provide information on nonradiative recombination involving defect levels. After understanding the challenges of applying PDS to materials emitting light, the advantages and features of PDS are described for evaluating the defect level in the bandgap. The reciprocal of the slope of the PDS spectrum near the bandgap energy (Urbach-like energy) increases with increasing In composition in InGaN films. With an increase of the Urbach-like energy, the radial distribution determined by X-ray absorption fine-structure spectroscopy is likely to decrease. This may be attributed to the random aggregation of In atoms in InGaN films. Also, it is proposed that the Urbach-like energy may be considered for discussing the in-gap emission.