The influence of gate length on the electron injection of velocity in an AlGaN/AlN/GaN НЕМТ channel

Abstract

Field-effect high-electron-mobility transistors (HEMTs) based on AlGaN/AlN/GaN heterostructures with various gate lengths L_g have been studied. The maximum values of current and power gaincutoff frequencies (f_T and f_max, respectively) amounted to 88 and 155 GHz for HEMTs with L_g = 125 nm, while those for the transistors with L_g = 360 nm were 26 and 82 GHz, respectively. Based on the measured S-parameters, the values of elements in small-signal equivalent schemes of AlGaN/AlN/GaN HEMTs were extracted and the dependence of electron-injection velocity v_inj on the gate–drain voltage was determined. The influence of L_g and the drain–source voltage on v_inj has been studied.