Postgrowth of a Si contact layer on an air-exposed Si_1-xGe_x/Si single quantum well grown by gas-source molecular beam epitaxy, for use in an electroluminescent device

A Si contact layer for an electroluminescent (EL) diode was successfully grown on a Si_1-xGe_x/Si single quantum well (SQW) layer by 'hybrid' Si molecular beam epitaxy (MBE). The 'hybrid' MBE was performed by growing the Si contact layer in a solid-source MBE chamber after transferring the sample through air from a gas-source MBE (GSMBE) chamber in which the starting SQW layer was initially grown by using disilane (Si₂H₆) and germane (GeH₄). The growth characteristics of the hybrid MBE were investigated by in situ monitoring of the reflection high energy electron diffraction. A (2×1) reconstruction was observed even after the sample was exposed to air for up to 15 h on a GSMBE-prepared Si(100) surface. Evidence of the excellent quality of the EL device was provided by the sharpest emission lines, a full width at half maximum of ≈5.5 meV. The spectra features of the EL and photoluminescence were found to be almost identical, and a well-resolved acoustic phonon replica was observed. Linear polarization for a no-phonon replica of EL was also observed along SQW plane.