Noise characterization of enhancement-mode AlGaN graded barrier MIS-HEMT devices

摘要

This paper reports a systematic theoretical study on the microwave noise performance of graded AlGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MIS-HEMTs) built on an Al_2O_3 substrate. The HfAlO_x/AlGaN/GaN MIS-HEMT devices designed for this study show an outstanding small signal analog/RF and noise performance. The results on 1 μm gate length device show an enhancement mode operation with threshold voltage, V_T= + 5.3 V, low drain leakage current, I_(ds,LL) in the order of 1 x 10~(-9) A/mm along with high current gain cut-off frequency, f_T of 17 GHz and maximum oscillation frequency f_(max) of 47 GHz at V_(ds) = 10 V. The device I-V and low-frequency noise estimation of the gate and drain noise spectral density and their correlation are evaluated using a Green's function method under different biasing conditions. The devices show a minimum noise figure (NF_(min)) of 1.053 dB in combination with equivalent noise resistance (R_n) of 23 Ω at 17 GHz, at V_(gs) = 6 V and V_(ds) = 5 V which is relatively low and is suitable for broadband low-noise amplifiers. This study shows that the graded AlGaN MIS-HEMT with HfAlO_x gate insulator is appropriate for application requiring high-power and low-noise.