Monolithic two-color short-wavelength InGaAs infrared photodetectors using InAsP metamorphic buffers

A bias-selectable two-color heterojunction bandgap engineered InGaAs thin film infrared photodetector, monolithically grown on an InP substrate by metal-organic chemical vapor deposition, is demonstrated. The detector structure has two back-to-back diodes, with In0.53Ga0.47As and In0.83Ga0.17As absorbers separated by n(+)-InAsxP1-x metamorphic buffers to accommodate for the lattice mismatch between the absorbers of similar to 2%. The surface of the topmost metamorphic buffer of InAs0.63P0.37, acting as a lattice-matched virtual substrate for the In0.83Ga0.17As absorber, has a Gaussian height distribution with a low surface roughness of 2.8 nm. The InAsxP1-x buffers achieve a gradual lattice constant transition from In0.53Ga0.47As to In0.83Ga0.17As, with a sufficient strain relaxation of 97%. Compared to the In0.53Ga0.47As diode, the In0.83Ga0.17As diode shows a higher reverse saturation current density by a factor of approximately 10(4), owing to a shorter minority carrier lifetime and a higher intrinsic carrier concentration. The bias-dependent two-color detection at the cutoff wavelengths of 1.7 mu m and 2.6 mu m is achieved, enabled by the In0.53Ga0.47As (blue channel) and In0.83Ga0.17As (red channel) absorption, respectively. The two-color InGaAs photodetector exhibits high specific detectivities of 4.1x10(11) and 3.1x10(9) cm.Hz(1/2)/W at 300 K in both the blue and red channel regions, respectively.