Effects of buffer doping on the strain relaxation of metamorphic InGaAs photodetector structures

Abstract The strain relaxation behaviors of metamorphic In0.83Ga0.17As photodetector structures on Si-doped, Be-doped and undoped InxAl1-xAs graded buffers are investigated. The cross-hatch period and surface roughness are increased by doping in buffer layers. X-ray diffraction reciprocal space mapping measurements reveal that the doping of Si and Be induces the increase of misfit dislocation density along [1−10] and [110] directions, respectively. The photoluminescence intensity of In0.83Ga0.17As photodetector structures is deteriorated by the doping in InxAl1-xAs buffers. The dark currents of fabricated photodetector chips are characterized and the In0.83Ga0.17As photodetector on undoped InAlAs buffer shows the lowest dark currents. The Si doping shows more detrimental effects on photoluminescence and dark current performances than Be doping due to the enhanced growth roughness. These results indicate that the doping of buffer layers is critical for the design and fabrication of metamorphic optoelectronic devices.