Polarization engineering of two-dimensional electron gas at ε-(AlxGa1-x)2O3/ε-Ga2O3 heterostructure

In this study, we present an investigation of the spontaneous and piezoelectric polarization in the epsilon-(AlxGa1-x)(2)O-3/epsilon-Ga2O3 heterostructures using density functional theory calculations. The spontaneous polarization (P-sp) was found to increase from 23.93 to 26.34 mu C/cm(2 )when Al-content increase from 0% to 50%. With Al-content increasing, the strain-induced piezoelectric polarization (P-pe) increases, which negates the P-sp, causing the total polarization (P-tot) of the epitaxy layer in the AlGaO/GaO heterostructure to remain almost constant across all Al compositions. Additionally, due to the ferroelectric nature of epsilon-Ga2O3, a high-density polarization-induced two-dimensional electron gas (2DEG) can be formed at the interface of polarization reversed epsilon-(AlxGa1-x)(2)O-3/epsilon-Ga2O3 when an electric field is applied. Using the 1D Schrodinger-Poisson model, the 2DEG of polarization reversed epsilon-(Al0.125Ga0.875)(2)O-3/epsilon-Ga2O3 was found to be 2.05 x 1014 cm(-2), which is nearly ten times larger than that of GaN-based structures. Our work indicates that epsilon-(AlxGa1-x)(2)O-3/epsilon-Ga2O3 heterostructure could play a key role attributed to the large polarization and capability in modulating the polarization for high-power electronic and radio frequency device applications.