Study on the negative transconductance behaviour in GaAs/AlGaAs based HEMT

Abstract

Abstract The present work intends on reinvestigating the origin of high gate voltage induced negative transconductance characteristics in a GaAs/AlGaAs based High Electron Mobility Transistor (HEMT), as the AlGaAs barrier layer thickness is reduced from 30 nm down to 10 nm. Apart from the decrease in the gate voltage range witnessing positive transconductance, an unprecedented decrement in the slope of positive transconductance is also observed as the barrier layer thickness is scaled down to 10 nm. With such observations in hand, a new fundamental challenge to the scaling of the hetero-layers is raised. This report mainly intends on explaining this transconductance behaviour of the HEMT, using the 3D conduction band energy profile of the barrier layer and the electron density profile of the GaAs channel layer, as provided by TCAD simulations. A high degree of correlation is observed between the transconductance behaviour of the HEMT and the relative difference in the conduction band energies of the Schottky interface and the hetero-interface. The significance of the conduction band energy difference of the barrier layer at gate and drain regions, over the negative drain current is also discussed further in the above context.