Lucky drift theory applied to InP/GaInAs and AlInAs/GaInAs multilayer avalanche photodetectors

A theoretical analysis of the ionisation characteristics of InP/Ga _0.47In_0.53As, Al_0.48In_0.52As/Ga_0.47In_0.53 As and InP/Ga_0.8In_0.2As multilayer avalanche photodiodes has been carried out using lucky drift theory. For the first time the effect of quantisation on the effective band-offsets is included. Even when quantisation is taken into account, results indicate that InP/Ga_0.47In_0.53As will not be a suitable low-noise APD structure, with a predicted value of β/α≈1-2; a result in agreement with earlier experimental and theoretical work. However, Al_0.48In_0.52As/Ga _0.47In_0.53As APDs are predicted to have α/β≈20-30 at useful values of gain, again in close agreement with experimental results; and modelling shows that quantisation should be avoided to maximise noise improvements. Lucky drift theory has thus shown its potential as a simple predictor of α/β in multilayer structures and when applied to the novel structure of an InP/Ga_0.8In_0.2As multilayer APD, lucky drift theory predicts β/α≈20 at M≈10