High electron density β-(Al0.17Ga0.83)2O3/Ga2O3 modulation doping using an ultra-thin (1 nm) spacer layer

This report discusses the design and demonstration of β-(Al0.17Ga0.83)2O3/Ga2O3 modulation doped heterostructures to achieve high sheet charge density. The use of a thin spacer layer between the Si delta-doping and the heterojunction interface was investigated in a β-(AlGa)2O3/Ga2O3 modulation doped structure. It is shown that this strategy enables a higher two-dimensional electron gas (2DEG) sheet charge density up to 4.7 × 1012 cm−2 with an effective mobility of 150 cm2/V s. The presence of a degenerate 2DEG channel was confirmed by the measurement of a low temperature effective mobility of 375 cm2/V s and the lack of carrier freeze out from low temperature capacitance voltage measurements. The electron density of 4.7 × 1012 cm−2 is the highest reported 2DEG density obtained without parallel conducting channels in a β-(AlxGa(1−x))2O3/Ga2O3 heterostructure system.