Role of satellite valleys in ionisation rate enhancement in multiple quantum well avalanche photodiodes

The enhancement of the electron ionisation rate in multiple quantum well avalanche photodiodes is determined by the band offsets in the satellite valleys rather than the Gamma valley as previously assumed for semiconductors where the threshold field for the Gunn effect is less than that for impact ionisation. Monte Carlo calculations in a model GaAs/Al_0.45Ga_0.55As heterostructure show no enhancement caused by the band offsets.