Optical characterization of InAlN/AlN/InGaN/GaN/sapphire high electron mobility transistor structures

Photoluminescence (PL) and Photoluminescence Excitation (PLE) measurements are performed on MOVPE grown InAlN/AlN/InGaN/GaN/Sapphire High Electron Mobility Transistor Structures. Features associated with InAlN barrier layer, InGaN channel layer and GaN buffer layer are clearly seen in the PL spectra. A blueshift of PL features with excitation intensity is observed which is claimed to be the signature of 2-dimensional electron gas formed in InGaN layer. By comparing the integrated intensity of PL peaks recorded at 7K and room temperature, it is confirmed that the optical quality of InGaN and GaN layers is superior when compared with that of InAlN barrier layer in the HEMT structure. It is also seen that the PLE features of InGaN channel layer are considerably red shifted with respect to PL features of the same layer. It is explained by considering the screening of polarization induced electric field causing a blue shift in case of PL measurements.