Ultrathin epitaxial germanium on crystalline oxide metal-oxide-semiconductor-field-effect transistors

Ultrathin films of single crystal Ge (100 Å or less) have been grown epitaxially on a lattice matched high-$\kappa$ crystalline oxide, lanthanum-yttrium-oxide, in turn grown on Si. Back-gated germanium-on-insulator field-effect transistors have been fabricated and measured from these germanium-on-insulator layers for Ge layers in the 30-600 Å range. The best devices exhibit an $I_{\text{on}}∕I_{\text{off}}$ ratio over ${10}^3$ at room temperature and ${10}^5$ at $T=77\mathrm{K}$ . These ultrathin devices can be fully depleted and inverted, enabling both $p$ and $n$ channel operation in the same device.