HTRB Stress Effects on Static and Dynamic Characteristics of 0.15 μm AlGaN/GaN HEMTs

High-temperature reverse bias (HTRB) stress effects on static and dynamic characteristics of 0.15 $\mu \text{m}$ AlGaN/GaN high-electron mobility transistors (HEMTs) are reported. The HEMTs were stressed to OFF-state bias ( $V_{\mathrm {GS}} \,\,=\,\,-7$ V and $V_{\mathrm {DS}} \,\,=$ 30 V) at a high temperature of 175 °C for 1000 h of duration. The HTRB-induced changes in drain current ( $I_{\mathrm {DS}}$ ) are analyzed. The $I_{G} - V_{G}$ characteristics are evaluated at $V_{\mathrm {DS}} \,\,=$ 0 V (emulating gate Schottky diode leakage) before and after the stress to examine the Schottky gate diode properties upon aging. The gate leakage current variations are further inspected with $V_{G}$ and $V_{D}$ sweeps. After aging test, a considerable drift in the output power ( $P_{\mathrm {out}}$ ) is observed during the interim RF measurement of the stressed HEMTs. The pulsed $I_{\mathrm {DS}} - V_{\mathrm {DS}}$ characteristics reveal the reduction in $I_{\mathrm {DS}}$ , particularly in the transition between linear and saturation regions; which is referred as knee-voltage smoothing. The output-admittance ( $Y_{22}$ ) and drain current transient (DCT) measurements are conducted to track any new defects created in the stressed HEMT and also assess the evolution of the pre-existing trap parameters. Especially, the physical location of the traps responsible for the knee-voltage smoothing and output power drift is identified by TCAD simulations.