Reduction of low-temperature nonlinearities in pseudomorphic AlGaAs/ingaas hemts due to si-related DX centers

The linearity of conventional pseudomorphic AlGaAs/InGaAs/AlGaAs high-electron mobility transistors with planar doping in the AlGaAs layers is shown to degrade at low temperatures down to -40°C, as measured by the adjacent-channel power ratio under wideband code-division multiple-access modulation. A modified structure, in which the planar Si doping layers are placed within thin single GaAs quantum wells inside the AlGaAs barrier layers, eliminates this degradation. Deep-level transient spectroscopy and persistent photocapacitance measurements show that trapping on DX centers is effectively eliminated. The linearity improvements are therefore attributed to the elimination of this trapping. Self-consistent solutions of the Schrdinger and Poisson equations show that the transfer of the donor electrons into the channel is essentially the same in the modified and conventional structures.