Photovoltaic effects on Franz-Keldysh oscillations in photoreflectance spectra: Application to determination of surface Fermi level and surface recombination velocity in undoped GaAs∕n-type GaAs epitaxial layer structures.

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We applied a Cat-CVD (catalytic chemical vapor deposition) passivation film to AlGaN/GaN HEMTs, to resolve the trade-off between their drain current transient time and gatedrain break down voltage. We did not employ any field plate because it degrades high frequency operation over C-band. The SiN passivation film, deposited after a NH 3 treatment, resulted in less transient time and less gate leakage current than conventional PE-CVD passivation. A T-shaped gate HEMT fabricated by this technique, with Lg = 0.4 µm and Wg = 50.4 mm, delivered an output power over 140 W (2.79 W/mm), which was a record power at C-band.

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