Two-color photovoltaic InGaAs infrared (IR) photodetectors with cutoff wavelengths of λc = 1.7 μm and 2.6 μm were monolithically grown on a single substrate by metal-organic chemical vapor deposition. The IR detectors have a back-to-back diode structure with In0.53Ga0.47As (Eg = 0.735 eV) and In0.83Ga0.17As (Eg = 0.488 eV) absorbers with a large lattice-mismatch of ~2%, using step-graded metamorphic InAsxP1-x buffers. The surface roughness and crystal quality of the metamorphic InAsP buffers were investigated by atomic force microscopy and X-ray diffractometry. The InAs0.63P0.37 topmost buffer achieved a low rms surface roughness of 2.8 nm and a sufficient strain relaxation of 97%. Photodetector devices were fabricated with a two-terminal configuration, providing a bias-dependent two-color detection in the short-wavelength IR (SWIR) spectral region (1–3 μm). The dark current densities of the In0.53Ga0.47As diode (blue channel) and In0.83Ga0.17As diode (red channel) were saturated at 1.8×10-8 and 1.1×10-4 A/cm2 at 300 K, respectively. The larger saturated current density in the red channel is due to higher Shockley-Read-Hall recombination and higher intrinsic carrier concentration. The two-color InGaAs detector showed high room-temperature specific detectivities of 4.1×1011 and 3.1×109 cm·Hz1/2/W for the blue (In0.53Ga0.47As) and red (In0.83Ga0.17As) channels, respectively. Our two-terminal InGaAs detector with SWIR two-color detection capability can be easily integrated in commercial two-terminal readout integrated circuits, leading to the realization of high-performance uncooled two-color IR imagers.
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