Strategies for direct monolithic integration of Al{sub}xGa{sub}(1-x)As/In{sub}Ga(1-x)As LEDS and lasers on Ge/GeSi/Si substrates via relaxed graded Ge{sub}xSi{sub}(1-x) buffer layers

摘要

Al{sub}xGa{sub}(1-x)As/GaAs quantum well lasers have been demonstrated via organometallic chemical vapor deposition (OMCVD) on relaxed graded Ge/Ge{sub}xSi{sub}(1-x) virtual substrates on Si. Despite un-optimized laser structures with high series resistance and large threshold current densities, surface threading dislocation densities as low as 2×10{sup}6 cm{sup}(-2) enabled cw room-temperature lasing at a wavelength of 858nm. The laser structures are oxide-stripe gain-guided devices with differential quantum efficiencies of 0.16 and threshold current densities of 1550A/cm{sup}2. Identical devices grown on commercial GaAs substrates showed differential quantum efficiencies of 0.14 and threshold current densities of 1700A/cm{sup}2. This comparative data agrees with our previous measurements of near-bulk minority carrier lifetimes in GaAs grown on Ge/GeSi/Si substrates. A number of GaAs/Ge/Si integration issues including thermal expansion mismatch and Ge autodoping behavior in GaAs were overcome.