Material optimization for extended short-wavelength and mid-wavelength infrared avalanche photodiodes

An ensemble Monte Carlo framework is used to compare the impact ionization behavior important to avalanche photodiode (APD) performance in a band-engineered InAlAs/InAsSb type-II superlattice with same-energy gap bulk InAs and HgCdTe at 250 K. Impact ionization rates are computed directly from the electronic band structures. The same stochastic transport kernel is used for each material for consistency. A realistic treatment of impact ionization initial and final carrier states is employed in the transport simulations that considers energy and crystal momentum conservation. The major effects of band features on carrier states, transit path lengths between impact ionization events, and impact ionization coefficients support the role of band engineering in materials selection for high-performance APDs.