Vertical integration of a GaAs/AlGaAs quantum-welllaser and along-wavelength quantum-well infra-red photodetector

Abstract
A short-wavelength (~0.8 µm) GaAs/AlGaAs graded-index separate-confinement heterostructure quantum-well laser has been monolithically integrated with a long-wavelength (~8 µm) GaAs/AlGaAs multiquantum-well infra-red photodetector on a semi-insulating GaAs substrate by molecular beam epitaxy. The vertical integration method is used and the combined structure is a pinin structure. Both the laser and detector exhibit excellent characteristics. At room temperature, the ridge waveguide laser has an extremely low threshold current of 25 mA and a differential quantum efficiency above 65% with a stripe width of 20 µm. The quantum-well detector has a peak response at 8 µm and a responsivity of 0.7 A/W.