In-situ strain control in epitaxial silicon carbide compound semiconductor.

Residual strain in an epilayer grown on a foreign wafer induces epiwafer's bow, that is often considered undesirable. Wafer bow however, can be advantageous because both the direction and magnitude of strain are vital for the fabrication of various Micro Electro Mechanical Systems (MEMS), such as resonators. Here strain control is reported for highly mismatched heteroepitaxy of cubic silicon carbide (3C-SiC) compound semiconductor on silicon (Si), a prized functional material, dependent solely on carbon to silicon ratio (C/Si) during growth.

Two-dimensional localization in GeSn.

Localization behaviour is a characteristic feature of the-type GeSn quantum well (QW) system in a metal-insulator-semiconductor device. The transition to strongly localized behaviour is abrupt with thermally activated conductivity and a high temperature intercept of 0.12 ×at a hole carrier density 1.

Uprooting defects to enable high-performance III-V optoelectronic devices on silicon.

The monolithic integration of III-V compound semiconductor devices with silicon presents physical and technological challenges, linked to the creation of defects during the deposition process. Herein, a new defect elimination strategy in highly mismatched heteroepitaxy is demonstrated to achieve a ultra-low dislocation density, epi-ready Ge/Si virtual substrate on a wafer scale, using a highly scalable process. Dislocations are eliminated from the epilayer through dislocation-selective electrochemical deep etching followed by thermal annealing, which creates nanovoids that attract dislocations, facilitating their subsequent annihilation.

Ballistic One-Dimensional Holes with Strong g-Factor Anisotropy in Germanium.

We report experimental evidence of ballistic hole transport in one-dimensional quantum wires gate-defined in a strained SiGe/Ge/SiGe quantum well. At zero magnetic field, we observe conductance plateaus at integer multiples of 2 e/ h. At finite magnetic field, the splitting of these plateaus by Zeeman effect reveals largely anisotropic g-factors with absolute values below 1 in the quantum-well plane, and exceeding 10 out-of-plane.

Self-organised fractional quantisation in a hole quantum wire.

We have investigated hole transport in quantum wires formed by electrostatic confinement in strained germanium two-dimensional layers. The ballistic conductance characteristics show the regular staircase of quantum levels with plateaux at n2e /h, where n is an integer, e is the fundamental unit of charge and h is Planck's constant. However as the carrier concentration is reduced, the quantised levels show a behaviour that is indicative of the formation of a zig-zag structure and new quantised plateaux appear at low temperatures.