Temperature-dependent epitaxial evolution of carbon-free corundumα-Ga2O3 on sapphire

Unintentionally doped carbon impurities from organometallic precursors are primary sources of carrier compensation and mobility degradation in wide bandgap semiconductors, leading to lowered performance of power devices. To address this challenge, carbon-free α-Ga2O3 single crystalline thin-films were heteroepitaxially grown on sapphire substrates by using gallium inorganic precursors through mist chemical vapor deposition technique. Determined through temperature dependence of growth rates, three distinct growth regimes are identified: the surface reaction limited regime below 480°C, the mid-temperature mass-transport limited regime (480-530 °C) and the high temperature limited regime related to desorption or phase transition. With an optimized around 530 °C, the densities of screw and edge dislocations are reduced to 7.17×10^6 and 7.60×10^9 cm-2, respectively. Notably, carbon incorporation was eliminated in the α-Ga2O3 grown by inorganic GaCl3, as evidenced by the absence of carbon-related vibrational bands in Raman scattering analysis, while crystalline quality was comparable to that grown with organometallic precursors. The high solubility of GaCl3 in water is expected to enable the rapid growth of high-purity α-Ga2O3 with improved electronic performances. Keywords: ultrawide bandgap semiconductor, chemical vapor deposition, impurity contamination.