ABSTRACT
In a conventional photodiode, the responsivity and diffusion length are closely coupled and an increase in the absorber thickness much beyond the diffusion length may not result in the desired improvement in the signal-to-noise (S/N) ratio. This effect is particularly pronounced at high temperatures where diffusions lengths are typically reduced. Only charge carriers that are photogenerated at distance shorter than the diffusion length from junction can be collected. In high operating temperature (HOT) detectors, the absorption depth of long wavelength infrared (LWIR) radiation is longer than the diffusion length. Therefore, only a limited fraction of the photogenerated charge contributes to the quantum efficiency.
