Thermal-stability improvement of a sulfur-passivated InGaP/InGaAs/GaAs HFET

The temperature-dependent characteristics of an InGaP/InGaAs/GaAs heterstructure field-effect transistor (HFET), using the (NH₄) ₂S_X solution to form the InGaP surface passivation, are studied and demonstrated. The sulfur-passivated device shows significantly improved dc and RF performances over a wide temperature range (300-510 K). With a 1 × 100 - μm² gate-dimension HFET by (NH₄) ₂S_x treatment, the considerably improved thermal stability over dc performances including lower temperature variation coefficients on the turn-on voltage (-1.23 mV/K), the gate-drain breakdown voltage (-0.05 mV/K), the gate leakage current (1.04 μA/mm · K), the threshold voltage (-1.139 mV/K), and the drain-saturation-current operating regimes (-3.11 × 10 ^-4/K) are obtained as the temperature is increased from 300 to 510 K. In addition, for RF characteristics, the sulfur-passivated device also shows a low degradation rate on drain-saturation-current operating regimes (-3.29 × 10^-4/K) as the temperature is increased from 300 to 400 K. These advantages provide the promise for high-speed high-frequency high-temperature electronics applications.