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We study the breakdown characteristics and timing statistics of InP and In0.52Al0.48As single-photon avalanche photodiodes (SPADs) with avalanche widths ranging from 0.2 to 1.0 κm at room temperature using a random ionization path-length model. Our results show that, for a given avalanche width, the breakdown probability of In0.52Al0.48As SPADs increases faster with overbias than InP SPADs. When we compared their timing statistics, we observed that, for a given breakdown probability, InP requires a shorter time to reach breakdown and exhibits a smaller timing jitter than In0.52Al0.48As. However, due to the lower dark count probability and faster rise in breakdown probability with overbias, In0.52Al0.48As SPADs with avalanche widths ⩽ 0.5 μm are more suitable for single-photon detection at telecommunication wavelengths than InP SPADs. Moreover, we predict that, in InP SPADs with avalanche widths ⩽ 0.3 μm and In0.52Al0.48As SPADs with avalanche widths ⩽ 0.2 μm, the dark count probability is higher than the photon count probability for all applied biases. [ABSTRACT FROM AUTHOR]

A charge control model was used to simulate the sensitivity and responsivity in a range of photodetector configurations including heterojunction bipolar phototransistors (HPTs), PIN-HBT, and APDs. Our simulations enabled for the first time a direct comparison of the performance between these photodetectors to be made. Simulations have been performed at bit rates from 2 to 40 Gb/s using various combinations of device design parameters (layer thickness, source resistance, and dc base voltage). For a BER = 10-9 at 40 Gb/s the best sensitivity of approximately -20 dBm was achieved using an optimized APD-H]3T configuration, followed by sensitivities of approximately -14 dBm using optimized PIN-HBTs and HPTs. These results were found to agree well with published experimental data. [ABSTRACT FROM AUTHOR]