Abstract

The objective of this presentation is to compare the noise properties of superlattice avalanche photodiodes (SAPDs) with those of conventional avalanche photodiodes (CAPDs). SAPDs are heterostructure devices constructed in such a way that principally one kind of carrier impact-ionizes. We restrict our study to SAPDs that operate by means of carrier transport perpendicular to the superlattice planes. In principle, the use of such devices promises a reduction in the feedback noise associated with conventional two-carrier avalanche photodiodes. We present expressions for the excess noise factor F_e for two-carrier SAPDs in the presence of residual hole ionization. It turns out that even a small amount of hole ionization can lead to a large excess noise factor, thereby limiting the usefulness of the device. A general formula is presented for the variance of the current at the output of an avalanche photodiode in terms of the quantum fluctuations of the incident light and the excess noise factor. An important special case provides direct proportionality if the number of photons at the input to the detector is Poisson. Theoretical results are also presented for the gain distributions and electron-counting distributions of single-carrier SAPDs (in the absence of residual hole ionization).

© 1986 Optical Society of America