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We predict the formation of a polarization-induced two-dimensional electron gas (2DEG) at the interface of ε-Ga2O3 and CaCO3, wherein the density of the 2DEG can be tuned by reversing the spontaneous polarization in ε-Ga2O3, for example, with an applied electric field. ε-Ga2O3 is a polar and metastable ultra-wide band-gap semiconductor. We use density-functional theory (DFT) calculations and coincidence-site lattice model to predict the region of epitaxial strain under which ε-Ga2O3 can be stabilized over its other competing polymorphs and suggest promising substrates. Using group-theoretical methods and DFT calculations, we show that ε-Ga2O3 is a ferroelectric material where the spontaneous polarization can be reversed through a non-polar phase by using an electric field. Based on the calculated band alignment of ε-Ga2O3 with various substrates, we show the formation of a 2DEG with a high sheet charge density of 1014 cm−2 at the interface with CaCO3 due to the spontaneous and piezoelectric polarization in ε-Ga2O3, which makes the system attractive for high-power and high-frequency applications. [ABSTRACT FROM AUTHOR]

Defects in undoped GaInNAsSb thin film (i-GaInNAsSb) were investigated by junction-capacitance technique using admittance and transient photocapacitance (TPC) spectroscopy. An electron trap D2 was identified at 0.34 eV below the conduction band (EC) of i-GaInNAsSb using admittance spectroscopy. Optical transition of valance band (EV) electrons to a localized state OH1 (EV + 0.75 eV) was manifested in negative TPC signal. Combined activation energy of OH1 and D2 defect corresponds to the band-gap of i-GaInNAsSb, suggesting that OH1/D2 acts as an efficient recombination center. TPC signal at ∼1.59 eV above EV was attributed to the nitrogen-induced localized state in GaInNAsSb. [ABSTRACT FROM AUTHOR]