Event Details

Latest approaches to achieve deterministic impact ionization process in avalanche photodiodes

Abstract: Avalanche Photodiodes (APDs) are routinely used in high speed telecom. When operated in the so-called Geiger mode (GM), the GM-APDs are now used to detect single photon in quantum communication and quantum imaging systems. Reducing the randomness in the impact ionization process holds the key to achieving “noiseless” APDs and GM-APDs. In this talk, I will present research at Sheffield to develop APDs with negligible excess noise, very high gain at low applied bias and extremely high gain-bandwidth product (GBP). I will first present our effort to transform InAs, from a material that was generally associated with leaky diodes, to APDs with high gain, low noise (excess noise factor below 2) and high GBP of 580 GHz. When operated at 77 K to reduce the dark current, low photon levels down to ~35 photons per 50 mks pulse was detected. These were achieved by designing the InAs APDs such that only electrons will initiate impact ionization events.

In parallel to InAs, I will also present some recent progress made in AlGaAsSb, a highly promising material for direct replacement of InP to achieve significantly lower noise and higher GBP. The avalanche gain has much weaker dependence on temperature, the ratio of electron to hole ionisation coefficients over 100 can be achieved, the excess noise factor is comparable to Si APDs and much higher GBP than InP can be achieved.