Resonant enhancement of impact in Ga1−<i>x</i>Al<i>x</i>Sb

Abstract

Impact ionization coefficients α and β of Ga1−xAlxSb avalanche photodiodes were measured for 0⩽x&amp;lt;0.3. The hole ionization coefficient β shows a strong band-structure effect: a resonant enhancement at x=0.065 (300 K) due to initiation of the ionization process by holes from the spin-orbit splitoff valence band. β/α can exceed values of 20 when the spin-orbit splitting Δ is equal to the band-gap energy Eg (resonant condition). The hole ionization coefficient depends exponentially on the difference between energy and band-gap energy Ei−Eg.