Enhanced effect of side-Ohmic contact processing on the 2DEG electron density and electron mobility of In0.17Al0.83N/AlN/GaN heterostructure field-effect transistors

Abstract

From the capacitance–voltage curves and current–voltage characteristics of the In0.17Al0.83N/AlN/GaN heterostructure field-effect transistors (HFETs) with side-Ohmic contacts and normal-Ohmic contacts, two-dimensional electron gas (2DEG) electron mobility was calculated. It is found that the polarization Coulomb field scattering (PCF) is closely related to the normal-Ohmic contact processing, and the PCF was weakened by side-Ohmic contact processing in In0.17Al0.83N/AlN/GaN HFETs, similar to that in AlGaN/AlN/GaN HFET devices. Further, due to the stronger spontaneous polarization in the thinner In0.17Al0.83N barrier layer, the influence of the gate bias on the PCF in In0.17Al0.83N/AlN/GaN HFETs is greater than that in AlGaN/AlN/GaN HFETs. As a result, the PCF in In0.17Al0.83N/AlN/GaN HFETs with side-Ohmic contacts is stronger than that in AlGaN/AlN/GaN HFETs with side-Ohmic contacts. Moreover, the 2DEG electron density in the In0.17Al0.83N/AlN/GaN HFETs with side-Ohmic contacts is increased by more than twice compared with the 2DEG electron density in the In0.17Al0.83N/AlN/GaN HFETs with normal-Ohmic contacts.