Improved Electron Mobility Higher than 10⁶ cm²/Vs in Selectively Doped GaAs/N-AlGaAs Heterostructures Grown by MBE

Electron mobility of quasi-two dimensional electron gas (2DEG) in selectively doped GaAs/ N -Al x Ga 1- x As ( x =0.3) heterostructures grown by MBE was investigated as a function of thickness of an undoped Al x Ga 1- x As spacer-layer (0–200 Å) introduced between a Si-doped AlGaAs layer and an undoped GaAs layer, at 77 K and 5 K. Mobility of 2DEG as high as 2,120,000 cm 2 /Vs at 5 K was achieved with a spacer-layer thickness of 200 Å. This electron mobility is higher than any observed so far in semiconductor materials.