Origin of Low-Frequency Negative Transconductance Dispersion in p-HEMT

TL;DR

This paper investigates the origin of low-frequency negative transconductance dispersion in p-HEMTs, identifying defect states at the hetero-interface and proposing a mobility degradation model involving ionized impurity scattering.

Contribution

It introduces a mobility degradation model that explains transconductance dispersion through interface defect states and their impact on 2DEG mobility.

Findings

Defect states are present at the AlGaAs/InGaAs interface.

Low-frequency transconductance dispersion is linked to mobility degradation.

A model explains the observed phenomena via ionized impurity scattering.

Abstract

Measurements of low-frequency transconductance dispersion at different temperatures and conductance deep level transient spectroscopic(CDLTS) studies of an AlGaAs/InGaAs pseudomorphic HEMT were carried out. The experimental results show the presence of defect states at the AlGaAs/InGaAs hetero-interface. A mobility degradation model was developed to explain the low frequency negative transconductance dispersion as well as the apparent hole-like peaks observed in the CDLTS spectra. This model incorporates a time dependent change in 2DEG mobility due to ionised impurity scattering by the remaining charge states at the adjoining AlGaAs/InGaAs hetero-interface.