  Avalanche photodiodes fabricated from AlInAsSb grown as a digital alloy
exhibit low excess noise. In this paper, we investigate the band
structure-related mechanisms that influence impact ionization. Band-structures
calculated using an empirical tight-binding method and Monte Carlo simulations
reveal that the mini-gaps in the conduction band do not inhibit electron impact
ionization. Good agreement between the full band Monte Carlo simulations and
measured noise characteristics is demonstrated.
