Interpretation of transconductance dispersion in AlGaAs/InGaAs pseudomorphic high electron mobility transistor by capacitance deep level transient spectroscopy

Abstract

The transconductance dispersion in AlGaAs/InGaAs PHEMT grown by MBE was interpreted by means of capacitance DLTS technique. When the gate bias was -0.2 V, the transconductance decreased at a very broad frequency range of 5.5 Hz -1.7x10(4) Hz. However, when a positive bias was applied to the gate, the transconductance increased at a lour frequency range and then decreased at a high frequency range. In the transconductance dispersion measurement as a function of temperature, the transition frequency shifted to higher frequency region with the increase in temperature. The emission energy for the change in the transition frequency was determined to be 0.394 eV from the temperature dependency of the transition frequency. In the capacitance DLTS measurements, we observed DX-center with thermal activation energy of 0.420 eV and two hole trap-like signals. The DX-center peak decreased as the filling pulse decreased from +0.6 V and disappeared at the bias of -0.1 V. Comparing the activation energy of DX-center in DLTS measurement with that obtained from the positive transconductance dispersion, we found that the DX-center led to the positive transconductance dispersion in the device.