Effect of HCl pretreatment on the oxide/semiconductor interface state density in AlGaN/GaN MOS-HEMT structures with MOCVD grown A12O3 gate dielectric

Suppression of surface donors (SDs) in AlGaN/GaN MOS-HEMTs represents a promising approach towards realization of normally-off switching devices with high threshold voltage. In this work, density of oxide/barrier interface traps (D_it) was determined in AlGaN/GaN MOS-HEMT structures with different SDs density (Nds), resulted from HCl pre-treatment variation. The results suggest deteriorated interface quality for sample without HCl cleaning. D_it was found to increase from ~10¹² to ~10¹³ eV^-1 cm^-2 in the energy range of 0.8 to 1.1 eV below the conduction band edge for structures with and without HCl cleaning step, respectively. On the other hand, our analysis indicates negligible contribution of interface traps to observed threshold voltage in thermal equilibrium. This indicates the nature of SDs to be different from that of interface traps.