The requirement for external quenching circuits adds substantially to the complexity and processing difficulty for InGaAs single-photon detectors, particularly in array configurations. Using bandgap engineering, we have developed InGaAs SPADs with self-quenching and self-recovering capabilities. The quenching process occurs in less than 100 ps, determined by the gain buildup time and the magnitude of device overbias. On the other hand, the recovery time is determined by the carrier escape time over an energy barrier that is typically tens of meVs. The recovery time can range from 1 ns to > 100 ns from the design of device and material structures. The optimal recovery time is a function of dark count rate and afterpulsing rate. Our data show that a recovery time of around 10 ns is near the optimum in most operation conditions. The self-quenched SPADs also show great suppression in excess noise, yielding a very uniform intensity distribution of output response to single photons. This unique property favors resolving photon number in an array device. As in conventional InGaAs SPADs, the single-photon detection efficiency increases with the amount of overbias (bias above breakdown voltage) and so does the dark count rate. A detection efficiency of 13-16% is obtained while still keeping the dark count and afterpulsing rates low. To our knowledge, the self-quenched InGaAs SPAD is the only device in its class to be able to operate under DC bias without gating or external circuits. As a result, the device is particularly suitable for array structures often used in communications, sensing, and imaging.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.