Improved 2DEG Mobility in Inverted GaAs/n-AlGaAs Heterostructures Grown by MBE

Electrical properties of an inverted heterojunction interface in selectively Si-doped GaAs/n-AlGaAs heterostructures were investigated. It was found that the origin of reduced 2DEG mobility in an inverted heterostructure is not interface roughness and/or background impurity pileup at the interface, but is diffused profile of doped Si impurities. Larger enhancement of 2DEG mobility at low temperature was obtained even in an inverted heterostructure by introducing a thick undoped AlGaAs spacer layer ( Δ t =100 Å) and lowering doping concentration of Si ( N d =5×10 17 cm -3 ); electron mobility as high as 7×10 4 cm 2 /Vs was observed at 5K with sheet electron concentration of 1×10 12 cm -2 .