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

The effects of deep levels on the transconductance dispersion in an AlGaAs/ InGaAs pseudomorphic high electron mobility transistor was interpreted usin g capacitance deep level transient spectroscopy (DLTS). Transconductance wa s decreased by 10% in the frequency range of 10 Hz-10 kHz at the negative g ate bias, but it was increased at the positive one. In the DLTS spectra, tw o hole trap-like signals corresponding to surface states were only observed at the negative pulse bias, whereas the DX-center with the activation ener gy of 0.42 +/- 0.01 eV were observed at the positive one. The activation en ergy agrees well with that obtained from the temperature dependence of the positive transconductance dispersion, 0.39 +/- 0.03 eV. These provide evide nce that the positive and negative transconductance dispersions are due to the DX center and surface states, respectively. (C) 1999 American Institute of Physics. [S0003-6951(99)04437-X].