Effects of deep levels on transconductance dispersion in AlGaAs/InGaAs pseudomorphic high electron mobility transistor

Abstract

The effects of deep levels on the transconductance dispersion in an AlGaAs/InGaAs pseudomorphic high electron mobility transistor was interpreted using capacitance deep level transient spectroscopy (DLTS). Transconductance was decreased by 10% in the frequency range of 10 Hz-10 kHz at the negative gate bias, but it was increased at the positive one. In the DLTS spectra, two hole trap-like signals corresponding to surface states were only observed at the negative pulse bias, whereas the DX-center with the activation energy of 0.42 +/- 0.01 eV were observed at the positive one. The activation energy agrees well with that obtained from the temperature dependence of the positive transconductance dispersion, 0.39 +/- 0.03 eV. These provide evidence that the positive and negative transconductance dispersions are due to the DX center and surface states, respectively.