In0.48Al0.52P/In0.2Ga0.8As pseudomorphic modulation-doped field-effect transistors (MODFETs) were realized for the first time by gas-source molecular beam epitaxy on GaAs substrates. Extrinsic transconductances of 173 and 283 mS/mm at 300 and 77 K, respectively, were measured for MODFETs with a 1 μm long and 75 μm wide gate. The devices showed very good pinch-off characteristics, and the output conductance was only 1.3 mS/mm. Extremely high Schottky barrier height (0.92 eV) and low gate leakage current (Irev<250 nA at VGS=-5 V) were achieved. The gate breakdown voltage was -17 V. No I-V collapse was observed at 77 K. Microwave measurements showed that the current gain cutoff frequency fT of the devices was 11.5 GHz and the maximum frequency of oscillation fmax, was 26 GHz. These results demonstrate the promising potential of pseudomorphic In0.48Al0.52P/InGaAs MODFETs as high frequency and high power devices.
