Monolithic growth of GaAs laser diodes on Si(001) by optimal AlAs nucleation with thermal cycle annealing

2021 
A GaAs quantum-well laser diode was directly grown on silicon (001) substrate by a hybrid technique comprising AlAs nucleation and thermal cycle annealing. The hybrid technique provided the advantages of superior surface roughness, high quantum efficiency, and low threading dislocation density (TDD) of a thin buffer. The TDD was quantitatively characterized through the electron channeling contrast imaging method. Directly grown GaAs on Si exhibited a TDD of 5.45 × 107 /cm2 with small thickness of approximately 1.5 µm. The roughness and quantum efficiency of GaAs on Si was enhanced by adopting the nucleation layer of AlAs. We found that there exists an optimal thickness of AlAs nucleation to be 1.68 nm through structural and optical analysis. Based on optimized GaAs on Si, the GaAs quantum-well laser diode was directly grown with a TDD of 2.5 × 107 /cm2. Whole epitaxial layers were grown by metalorganic chemical vapor deposition. An edge-emitting broad stripe laser diode was successfully fabricated with a cavity length and width of 1120 µm and 60 µm, respectively. The continuous-wave lasing at room temperature was realized with a threshold current density of 643 A/cm2 and maximum output power of 19.7 mW at a single facet, where a threshold current density of 317 A/cm2 was obtained under pulsed operation condition. This result would constitute a building block to realize silicon-based on-chip light sources.
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