Optical and microwave performance of GaAs-AlGaAs and strained-layer InGaAs-GaAs-AlGaAs graded-index separate-confinement heterostructure single quantum well lasers

The authors have fabricated InGaAs-GaAs-AlGaAs strained-layer graded-index separate-confinement-heterostructure (GRINSCH) quantum-well lasers grown by molecular beam epitaxy (MBE). Use of optimized growth conditions resulted in low-threshold performance. The lasers emit at a wavelength of 1.03 μm and have threshold currents of 12 mA for 3-μm×400-μm devices and threshold current densities of 168 A/cm² for 150-μm×800-μm devices. They emit at longer wavelengths and have lower threshold currents than previously reported strained-layer lasers grown by MBE and have threshold currents below those of strained-layer lasers grown by OMVPE (organometallic vapor-phase epitaxy). Measurements of threshold current and microwave modulation response have been performed on strained-layer InGaAs and unstrained GaAs GRINSCH SQW (single-quantum-well) lasers with identical cladding and graded regions grown by molecular beam epitaxy. They confirm the lower threshold currents and higher modulation bandwidths that have been theoretically predicted for strained-layer lasers