Low-Noise Avalanche Photodiodes for Midwave Infrared (2 to 5 um) Applications

摘要

Report developed under STTR contract for topic AF04-T021. We have developed a mid-wave infrared (MWIR) avalanche photodiode (APD) based on a GaInAs/GaAsSb superlattice absorption region that is compatible with InP substrates. This superlattice structure exhibits a photodetection cutoff wavelength of approximately 2.5 microns when lattice-matched to InP, and our calculations show the introduction of compensated strain can provide cutoff wavelengths as long as -5 microns. Using the lattice-matched superlattice in a p-i-n structure, we have demonstrated 43% quantum efficiency at 2.23 microns, a low dark current density of 1E-5 A/sq cm, and a peak detectivity of 7E10 cm (Hz/W)(exp 1/2), all at a temperature of 200 K, accessible using thermoelectric coolers. By incorporating this superlattice into an APD structure with an InP multiplication region, we have fabricated 160 micron diameter MWIR APDs exhibiting a gain of 50 and an operating dark current of less than 100 nA at 240 K. Smaller 36 micron diameter devices of the same structure exhibit sub- nanoampere dark currents below approximately 225 K.