Two-dimensional numerical simulation of Fermi-level pinning phenomena due to DX centers in AlGaAs/GaAs HEMTs

Abstract

Abstract-Fermi-level pinning phenomena due to DX centers in AlGaAs/GaAs HEMT's are analyzed using two-dimensional numerical simulation based on a drift-diffusion model. A DX center model is introduced assuming Fermi-Dirac statistics for ionized donor density with the aluminum mole fraction dependence of the deep-donor energy level. The calculated results reveal that the decrease in transconductance of AlGaAs/GaAs HEMT's in a high gate-bias region is caused by the existence of DX centers. This is because the Fermi level is pinned at deep donor levels in the n-AIGaAs layer. Furthermore, the superiority of AlGaAs/InGaAs pseudomorphic HEMT's is discussed in terms of the Fermi-level pinning.

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