We identify a new shot noise suppression mechanism in a thin ($\sim 100\mathrm{nm}$) heterostructure avalanche photodiode. In the low-gain regime the shot noise is suppressed due to temporal correlations within amplified current pulses. We demonstrate in a Monte Carlo simulation that the effective excess noise factors can be $<1$, and reconcile the apparent conflict between theory and experiments. This shot noise suppression mechanism is independent of known mechanisms such as Coulomb interaction, or reflection at heterojunction interfaces.

• Received 5 April 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.176604