Ga composition effects on the electrical parameters of (Al,Ga)Sb/InAs two-dimensional electron gas

Abstract The effects of Ga composition on the electrical parameters of (Al,Ga)Sb/InAs two-dimensional electron gas have been investigated. The (Al,Ga)Sb/InAs structures are grown on GaAs (001) substrate by molecular-beam epitaxy with various Ga compositions in Al 1− x Ga x Sb bottom barrier. The sheet resistance shows a crossover with the variation of temperature, and the temperature T * corresponding to this crossover decreases with increasing the Ga composition. The temperature dependence of the electron mobility is similar for the samples with different Ga compositions, while the temperature dependence of the carrier density is obviously different. Qualitative analyses reveal that the temperature dependent portion of carrier density is mainly determined by the interface-related donors. A thermal activation model is used to fit the temperature dependence of carrier density, and the fitting results imply that the thermal activation energies of the carriers are significantly affected by the Ga composition. Our results provide useful information for understanding the sources of carriers in the (Al,Ga)Sb/InAs systems, and provide one pathway for the modulation of the temperature dependent carrier density.