Multivalley Electron Conduction at the Indirect-Direct Crossover Point in Highly Tensile-Strained Germanium

For applications such as low-power tunneling transistors and memory, lasers, qubits, and spintronics, there is interest in using strain to enhance carrier mobility in semiconductors. This experimental and theoretical study investigates transport in highly strained germanium, in which multivalley electron conduction emerges. Surprisingly, all conduction occurs via the L valley in Ge for biaxial tensile strain below 1.6%, while above the contribution from the \ensuremath{\Gamma} valley increases, with negligible contributions from the underlying strain template.