Impact Ionization Enhancements In Alxga1-Xsb Avalanche Photodiodes

The apparent inconsistency among several experiments examining the presence of an enhanced hole to electron impact ionization coefficient ratio in AlxGa1-xSb is shown to be associated with the failure to recognize that measurements at high and low electric fields lead to physically different results. The ratio exhibits an enhancement only for low fields because of "resonant" band structure effects associated with the equality of the energy gap and the spin orbit splitting. This effect is shown to be unimportant at high fields. The impact ionization calculations utilize realistic pseudopotential band structure Coulomb scattering matrix elements. Effects associated with alloy scattering are found to be unimportant. (C) 2000 American Institute of Physics. [S0003-6951(00)04045-6].