Dependence of the Behavior of PN-photodiode Laser Detectors upon the Biasing Electric Field

Abstract

The behavior of a PN-photodiode and its dependence upon the biasing electric field are discussed theoretically by taking into consideration the hot electron mobility and the space charge effect in semiconductors. It is shown that the non-saturation photocurrent is directly proportional to the reverse bias field in the depletion-layer of the linear-graded junction diode. These theoretical results agree with our experimental results which were obtained using a ruby laser as the optical source. The photocurrent, reduction factors and transit phases, the latter two of which are a measure of the frequency response, are obtained in the case where light is incident parallel to the junction plane and the electric field is distributing parabolically in the depletion-layer. It is shown from this analysis that the parabolic field distribution gives smoother reduction profiles than a uniform field. The relation between the laser intensity and the optimum biasing electric field is given.