UV/blue GaP avalanche photodiodes

Gallium phosphide, though most commonly used in emitters, has potential for use in both ultraviolet, blue, and blue green light detection applications from 250 nm to 500 nm. In GaP, shorter wavelengths have a higher absorption coefficient and consequently a shorter absorption length. Therefore, increased quantum efficiency in the UV spectrum hinges on these carriers reaching the active region prior to recombination. Thus, we implemented a recessed window structure to reduce the p-region thickness, resulting in increased quantum efficiency at shorter wavelengths. An improved peak quantum efficiency of 38% occurs at ∼440 nm. It is also important to note the enhanced quantum efficiency at short wavelengths, especially those below the spectral range of the non-recessed devices.