The trap-related characteristics in depletion mode GaAs metal-oxide-semiconductor field-effect-transistors (MOSFETs) were studied using two different electrical characterization techniques of current collapse and low-frequency noise measurements. With a high-quality MBE-grown gate oxide layer Ga2O3(Gd2O3)similar to 30 nm thick in situ on GaAs, an extremely small drain current collapse factor Delta I-max of less than 5% was observed even with a high drain bias of 16 V. In addition, no kink effect was observed in the low-frequency AC I-V characteristics. Moreover, a normalized drain noise current spectral density in the range of 10(-11)-10(-9)Hz(-1) (at 10 Hz) was obtained, which is comparable to modern 0.13-mu m Si complementary MOS (CMOS) technology under similar biasing conditions. The results indicate low interfacial trap densities for the studied GaAs MOSFETs. (c) 2007 Elsevier B.V. All rights reserved.