Pseudomorphic and Metamorphic Quantum Dot Heterostructures for Long-Wavelength Lasers on GaAs and Si

We have investigated the design, molecular beam epitaxial growth, and fundamental characteristics of pseudomorphic and metamorphic quantum dot laser heterostructures on GaAs and Si. By utilizing the special techniques of low-temperature growth and in situ thermal annealing and carefully controlling various growth parameters, we have achieved 1.3-1.55-mum pseudomorphic and metamorphic quantum dot heterostructures on GaAs that exhibit superior optical quality. The special techniques of p-doping and tunnel injection have also been explored in the design and growth of quantum dot laser heterostructures, leading to long-wavelength lasers on GaAs that exhibit, for the first time, ultralow threshold current (J_th = 63 A/cm²), nearly temperature-invariant operation (T₀ ap infin), large modulation bandwidth (f_{-3 dB} = 11 GHz), near-zero alpha-parameter, and very small chirp (les0.2 A). With the incorporation of multiple layers of InAs quantum dots as effective three-dimensional dislocation filters, we have demonstrated the first room-temperature operational quantum dot lasers on Si that exhibit relatively low threshold current (J_th = 900 A/cm²) and very high temperature stability (T₀ = 244 K).