Theory of electron and hole impact ionization in quantum well and staircase superlattice avalanche photodiode structures

An ensemble many particle Monte Carlo simulation of both electron and hole impact ionization superlattice avalanche photodiodes is presented. The effects of the well depth, width, and applied electric field are analyzed for both the electrons and holes in the quantum well structure. The results are consistent with the current theory of impact ionization first proposed by Shichijo and Hess. It is found that the ratio of the electron to hole impact ionization rates is roughly two orders of magnitude in the staircase APD while α/β is enhanced by one order of magnitude in the quantum well device.