NOVEL GAAS PHOTODETECTOR WITH GAIN FOR LONG-WAVELENGTH DETECTION

A novel photodetector based upon annealed low temperature molecular beam epitaxy GaAs capable of detecting wavelengths out to 1.5 μm has been developed. The device utilizes a photoconductive detector with a high photo-generated carrier lifetime to transit time ratio in order to achieve a high internal gain. The sensitivity to illumination with photons of sub-bandgap energies is achieved due to the internal photo-emission from the semi-metallic arsenic precipitates. The device exhibits higher gains at lower input powers because the effective carrier lifetime is longer for lower input power levels. This variation in carrier lifetime can be explained in terms of the effectiveness of the arsenic precipitates as recombination centers as a function of optical power levels.