A 7-eV bandgap semiconductor based on silicon-doped α-(AlxGa1-x)2O3.

In rectifying power electronics, wider-bandgap (Eg) semiconductors allow higher efficiency and power density with the Baliga figure of merit proportional to Eg5.5 (refs. 1,2). Unfortunately, the unique ability of semiconductors to have their conductivities controllably modulated over orders of magnitude by equilibrium doping methods becomes increasingly elusive as the bandgap increases. Increasing demand for wider-bandgap semiconductors has led to many materials previously considered insulators-including GaN, SiC, AlN, Ga2O3 and GeO2-to emerge as useful semiconductors after decreasing defect densities and finding appropriate dopants. Here we report silicon-doped α-(AlxGa1-x)2O3 films with bandgaps exceeding 7.0 eV grown by suboxide molecular-beam epitaxy, surpassing that of cubic boron nitride, the next-widest-bandgap semiconductor known3-5. In the colossal-bandgap regime, >6 eV, our silicon-doped α-(AlxGa1-x)2O3 films have room-temperature conductivities over 100 million times higher than all previous reports6. We fabricate a Schottky diode and a field-effect transistor (the AlphaFET) with colossal-bandgap channels. These α-(AlxGa1-x)2O3 films and devices use sapphire, an abundant, inexpensive substrate with excellent quality that is produced at massive scale, facilitating the development and adoption of colossal-bandgap electronics. Our achievement breaks the trend of increasing synthesis difficulty, cost and small size of ever-wider-bandgap semiconductors, for example, diamond and cubic boron nitride.