Band Alignment and Enhanced Interfacial Conductivity Manipulated by Polarization in a Surfactant-Mediated Grown κ-Ga2O3/In2O3 Heterostructure

Integration of intriguing ferroelectric kappa-Ga2O3 on other oxide semiconductors opens an exciting avenue to invoke emergent transport phenomena and enable rational design of advanced device architectures, whereas the fundamental growth dynamics and physical properties of metastable kappa-Ga2O3, are still far unexplored. In this work, we report on the heterostructure construction of single crystalline metastable orthorhombic kappa-Ga2O3 epilayers and cubic In2O3 (111) by means of laser molecular beam epitaxy. Elements of Sn and In are found to segregate to the growth surface and serve as surfactants to reduce the total surface energy and diffusion barrier of oxygen adatoms, hence producing Ga-rich conditions on the growth front, which in turn facilitates the stabilization of kappa-phase Ga2O3. Depth-profiled X-ray photoemission spectral (XPS) analysis identified a type-I band alignment with a conduction band offset (CBO) of 0.45 eV and a valence band offset (VBO) of -1.15 eV for a kappa-Ga2O3/In2O3 heterostructure. Determined by the analysis of Hall results with a double-layer model, a two-dimensional electron gas (2DEG) with a sheet carrier concentration of 1.2 X 10(14) cm(-2) and an enhanced mobility of 192 cm(2)/(V s) is confined at the heterostructure interface. The self-consistent Poisson-Schrodinger calculations indicate that the enhanced interfacial conductivity is a result of the combination of polarization manipulation and band discontinuity, well-supported by the characteristics of piezoelectric force microscopy and depth-profiled XPS. Integrating kappa-Ga2O3 on other hexagonal polar semiconductors may open a possibility to manipulate the interfacial conductivity through polarization engineering and deliver advanced devices with multiple functionalities.

Automated summary

This study successfully constructed the heterostructure of single crystalline metastable orthorhombic kappa-Ga2O3 epilayers and cubic In2O3 (111) using laser molecular beam epitaxy. Analysis of XPS and Hall results revealed the formation of a two-dimensional electron gas at the heterostructure interface with high carrier concentration and mobility.