Impact ionization coefficient ratio in InGaAs/InAlAs superlattice avalanche photodiodes determined from noise measurements

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Abstract
The noise of an In0.53Ga0.47As/In0.52Al0.48As superlattice avalanche photodiode is measured at 700 MHz as a function of applied reverse bias voltage. From the measured data the ratio k of the hole to electron impact ionization coefficients is determined. This ratio is equal to 6 in the field range (0.8–2.3)×105 V/cm; beyond this range k decreases with increasing field. The field dependence of k is attributed to a transition from ionization across the valence-band-edge discontinuity to band-to-band ionization.