Two-dimensional nitrides extend the β-Ga2O3 application by controlling the band levels in β-Ga2O3 based heterostructure

Modulating the surface band levels and transportation of β-Ga2O3 is vital to realize a high-performance β-Ga2O3 device, since the optoelectronic performance of the β-Ga2O3 device is greatly limited by the transportation barrier of β-Ga2O3 surface. Here, First-principles calculation results shows that, the up-bending conduction band of β-Ga2O3 surface can be transformed into down-bending with two-dimensional electron gas (2DEG)-like character upon forming β-Ga2O3/h-XN (X = B, Al, Ga) heterostructures, which can be further modulated and controlled by the external E-filed further. The band bending for β-Ga2O3/h-BN shows a variation tendency of “reduce slightly → reduce significantly → enhance”; while that of β-Ga2O3/h-AlN and β-Ga2O3/h-GaN shows a variation tendency of “enhance → reduce → enhance” when the external E-filed ranges from negative to positive value. Because these heterostructures show different charge transfers, tunneling barriers and built-in E-filed. Consequently, the type-II band alignment of β-Ga2O3/h-BN turns into type-I, while that of β-Ga2O3/h-AlN and β-Ga2O3/h-GaN change into reversed type-II character. In addition, 2DEG-like characters in these heterostructures are almost disappeared when the β-Ga2O3 surface is passivated by hydrogen due to the significantly reduced charge transfer. These findings provide a guideline to design and modulate the surface band levels and carrier transportation for the high-performance β-Ga2O3 device.