Wavelength extended InGaAs/InAlAs/InP photodetectors using n-on-p configuration optimized for back illumination

Using n-on-p InGaAs/InAlAs/InP heterojunction structure with relative thin Be doped linearly graded InxAl1−xAs as buffer layer, wavelength extended InGaAs photodiodes with 50% cutoff wavelength of 2.0 μm and 2.4 μm at room temperature have been grown by using gas source MBE with a convenient but reliable correlative ramping procedure, and their dark current performance in a wide temperature range have been investigated. For 300 μm diameter detectors at 290 K, typical R0A and dark current at 10 mV reverse bias are 760 Ωcm2/11.3 nA for cutoff wavelength of 2.0 μm, and 104 Ω cm2/75.1 nA for cutoff wavelength of 2.4 μm. Room temperature peak detectivity Dλp∗ reaches 1.3E11 cm Hz1/2/W and 6.5E10 cm Hz1/2/W, respectively measured using 900 K black body source. For back illumination the parameter optimization of n-on-p configuration is much easier than those of p-on-n, also the structure quality of the n-on-p is better than those of p-on-n because of the high Be doping in the linear graded buffer layer instead of Si.