InAs APD with solid state photomultiplier characteristics

InAs, with a bandgap of 0.35 eV can provide excellent light detection across the wavelengths from 1550-3500 nm. When operated as an avalanche photodiode (APD), its excess noise factor remains low at ~1.5 [1], independent of magnitude of the avalanche gain. This can be achieved by ensuring that the field is kept low such that hole impact ionization coefficient remains negligible [2]. Because of its electron-only ionization property, the avalanche duration in InAs electron-APD (e-APD) will be no more than two carrier transit times. Indeed, a very high gain-bandwidth-product of 580 GHz was demonstrated [3]. Therefore InAs e-APD has the potential to be developed into very high speed APD, high speed single photon detector and single photon detector for wavelengths above 1550 nm. In this paper, recent progress in InAs e-APD to achieve these aims is presented.