Design, Theoretical, and Experimental Investigation of Tensile-Strained Germanium Quantum-Well Laser Structure

Strain and band gap engineered epitaxial germanium (?-Ge) quantum-well (QW) laser structures were investigated on GaAs substrates theoretically experimentally for the first time. In this design, we exploit ability of an InGaAs layer to simultaneously provide tensile strain in Ge (0.7–1.96%) sufficient optical carrier confinement. The direct band-to-band gain, threshold current density (Jth), loss mechanisms that dominate ?-Ge QW structure calculated using first-principles-based 30-band k·p electronic theory, at injected concentrations from 3 × 1018 9 1019 cm–3. higher increases gain wavelengths; however, a decreasing thickness is required by due critical avoiding relaxation. addition, predict Jth 300 A/cm2 can be reduced <10 increasing 0.2% 1.96% lasing media. measured room-temperature photoluminescence spectroscopy demonstrated emission, conduction ?-valley heavy-hole (0.6609 eV) 1.6% tensile-strained Ge/In0.24Ga0.76As heterostructure grown molecular beam epitaxy, agreement with value theory. detailed plan-view transmission electron microscopic (TEM) analysis 0.7% 1.2% ?-Ge/InGaAs exhibited well-controlled dislocations within each layer. dislocation below 4 106 cm–2 layer, which upper bound, suggesting superior material quality. Structural realistic 1.95% biaxially strained In0.28Ga0.72As/13 nm ?-Ge/In0.28Ga0.72As Ge/In0.28Ga0.72As heterointerface minimal relaxation X-ray cross-sectional TEM analysis. Therefore, our monolithic integration ultimately transfer process Si substrate via InGa(Al)As/III–V buffer architecture would significant step toward photonic technology based platform.