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Current laser-based display and lighting applications are invariably using blue laser diodes (LDs) grown on free-standing GaN substrates, which are costly and smaller in size compared with other substrate materials.1–3 Utilizing less expensive and large-diameter Si substrates for hetero-epitaxial growth of indium gallium nitride/gallium nitride (InGaN/GaN) multiple quantum well (MQW) structure can substantially reduce the cost of blue LDs and boost their applications. To obtain a high crystalline quality crack-free GaN thin film on Si for the subsequent growth of a blue laser structure, a hand-shaking structure was formed by inserting Al-composition step down-graded AlN/AlxGa1−xN buffer layers between GaN and Si substrate. Thermal degradation in InGaN/GaN blue MQWs was successfully suppressed with indium-rich clusters eliminated by introducing hydrogen during the growth of GaN quantum barriers (QBs) and lowering the growth temperature for the p-type AlGaN/GaN superlattice optical cladding layer. A continuous-wave (CW) electrically pumped InGaN/GaN quantum well (QW) blue (450 nm) LD grown on Si was successfully demonstrated at room temperature (RT) with a threshold current density of 7.8 kA/cm2.

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Direct bandgap III-V semiconductor lasers grown on silicon (Si) are highly desired for monolithic integration with Si photonics. Fabrication of semiconductor lasers with a Fabry–Pérot cavity usually includes facet cleavage, however, that is not compatible with on-chip photonic integration. Etching as an alternative approach holds a great advantage in preparing cavity mirrors with no need of breaking wafer into bars. However, gallium nitride (GaN) sidewalls prepared by dry etching often have a large roughness and etching damages, which would cause mirror loss due to optical scattering and carrier injection loss because of surface non-radiative recombination. A wet chemical polishing process of GaN sidewall facets formed by dry etching was studied in detail to remove the etching damages and smooth the vertical sidewalls. The wet chemical polishing technique combined with dry etching was successfully applied to the on-wafer fabrication of cavity mirrors, which enabled the realization of room temperature electrically injected InGaN-based laser diodes grown on Si.

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We reported the successful growth of a crack-free high-quality 2 μm-thick Al0.5Ga0.5N film with a smooth surface grown on planar Si by metal–organic chemical vapor deposition.