Monolithic integration of a photodetector and a vertical-cavity surface-emitting laser

Monolithic integration of a photodetector with a vertical-cavity surface-emitting laser (SEL) is reported. The SELs lase at room temperature and emit a 850-nm highly coherent, low-divergence, circular beam directly from the top surface. The integrated photodetector shows a linear response to the laser emission with an effective responsivity of 0.25 A/W. The SEL consists of a GaAs multiquantum-well active region and doped Al/sub 0.15/Ga/sub 0.85/As/AlAs distributed Bragg reflectors (DBRs). Proton implantation was used to fabricate planar gain-guided lasers. Since the GaAs substrate is opaque to the lasing wavelength, the top mirror is designed to have lower reflectivity and annular contacts are used to permit emission from the top surface. After growing the SEL, additional i-GaAs and n-AlGaAs layers were grown on top of the p-doped DBR to form the p-i-n photodetector (PD).