In this work, an in situ SiO 2 passivation technique using atomic layer deposition (ALD) during the growth of gate dielectric TaSiO x on solid-source molecular beam epitaxy grown (100)In x Ga 1– x As and (110)In x Ga 1– x As on InP substrates is reported. X-ray reciprocal space mapping demonstrated quasi-lattice matched In x Ga 1– x As epitaxy on crystallographically oriented InP substrates. Cross-sectional transmission electron microscopy revealed sharp heterointerfaces between ALD TaSiO x and (100) and (110)In x Ga 1– x As epilayers, wherein the presence of a consistent growth of an ∼0.8 nm intentionally formed SiO 2 interfacial passivating layer (IPL) is also observed on each of (100) and (110)In x Ga 1– x As. X-ray photoelectron spectroscopy (XPS) revealed the incorporation of SiO 2 in the composite TaSiO x , and valence band offset (Δ E V ) values for TaSiO x relative to (100) and (110)In x Ga 1– x As orientations of 2.52 ± 0.05 and 2.65 ± 0.05 eV, respectively, were extracted. The conduction band offset (Δ E C ) was calculated to be 1.3 ± 0.1 eV for (100)In x Ga 1– x As and 1.43 ± 0.1 eV for (110)In x Ga 1– x As, using TaSiO x band gap values of 4.60 and 4.82 eV, respectively, determined from the fitted O 1s XPS loss spectra, and the literature-reported composition-dependent In x Ga 1– x As band gap. The in situ passivation of In x Ga 1– x As using SiO 2 IPL during ALD of TaSiO x and the relatively large Δ E V and Δ E C values reported in this work are expected to aid in the future development of thermodynamically stable high-κ gate dielectrics on In x Ga 1– x As with reduced gate leakage, particularly under low-power device operation.

Strain and bandgap engineered epitaxial germanium (ε-Ge) quantum-well (QW) laser structures were investigated on GaAs substrates theoretically and experimentally for the first time. In this design, we exploit the ability of InGaAs layer to simultaneously provide tensile strain in Ge (0.7% to 1.96%) and sufficient optical and carrier confinement. The direct band-to-band gain, threshold current density (Jth) and loss mechanisms that dominate in the ε-Ge QW laser structure, were calculated using first-principles-based 30-band k.p electronic structure theory, at injected carrier concentrations from 3x10 18 cm -3 to 9x10 19 cm -3 . The higher strain in ε-Ge QW increases the gain at higher wavelengths; however, a decreasing thickness is required by higher strain due to critical layer thickness for avoiding strain relaxation. In addition, we predict that a Jth of 300 A/cm 2 can be reduced to <10 A/cm 2 by increasing strain from 0.2% to 1.96% in ε-Ge lasing media. The measured room temperature photoluminescence spectroscopy demonstrated direct bandgap optical emission from the conduction band at valley to heavy-hole (0.6609 eV) from 1.6% tensile strained Ge/In0.24Ga0.76As heterostructure grown by molecular beam epitaxy, is in agreement with the value calculated using 30-band k.p

Group IV-based germanium-tin (Ge1-ySny) compositional materials have recently shown great promise for infrared detection, light emission and ultra-low power transistors. High carrier lifetimes are desirable for enhancing the detection limit...