Superconductivity in Quasi-2D Electron System with Ultra-high Electron Density

Superconductivity is widely observed in transition metals, but not easily obtained in conventional semiconductors such as Si or III-V compound semiconductors. Here we report the first electrical experiments performed at room pressure on a set of AlInN/AlN/GaN heterojunction samples with different electron doping concentrations. The state-of-the-art AlInN/AlN/GaN 2DEG grown by MOCVD for GaN HEMT applications has a high electron density of 2 $\times$ 10$^{13}$/cm$^{2}$ and it can be increased to 7 $\times$ 10$^{15}$/cm$^{2}$ by solid metal doping. With such 2-3 orders of magnitude higher electron density, superconducting state has been observed in the conventional III-V semiconductors with T$_{\mathrm{c}}$ $\sim$ 1K and two-step H$_{\mathrm{c}}$ of 0.3T and 1.5T with magnetic field parallel to the sample surface and H$_{\mathrm{c}}$ of 0.1T and 0.8T with magnetic field perpendicular to the sample surface. Angular dependence H$_{\mathrm{c}}$ reveals the quasi-2D nature of the electron system. More details of these new experiments related with superconducting III-V semiconductors will be presented.