On factors influencing Si segregation and its effect on the two-dimensional electron gas mobility in inverted GaAs/n-AlGaAs heterostructures

Abstract

The electrical properties of inverted GaAs/n-AlGaAs heterostructures grown at varying As-to-Ga (group V:III) flux ratios and Si doping concentrations in the AlGaAs layer were investigated. In these heterostructures, it was found that the two-dimensional electron gas (2DEG) mobility, as well as being affected by the Si doping level, is also strongly influenced by the group V:III flux ratio at which the structures are grown. The results indicate a significant contribution from a probable diffused profile of doped Si impurities in the AlGaAs spacer and GaAs channel layers resulting from Si surface segregation in the doped AlGaAs layer. This effect of Si segregation, which dominates at high Si doping levels, is greatly enhanced at lower group V:III flux ratios. At higher group V:III flux ratios of about 5.66 and low Si doping concentration ( N rmd = 3 × 10 17 cm -3) , a high 2DEG mobility of 5 × 10 4 cm 2 V -1 s -1 was achieved at 77 K, with an interface carrier density N rms ≈ 1.7 × 10 11 cm -2.