Performance characteristics of a pseudomorphic p-type, normal incidence, Ge0.25Si0.75/Si strained-layer quantum well infrared photodetector on (001) Si is described for 20≤T≤77 K. The device shows broadband photoresponse (8–14 μm) which is attributed to strain and quantum confinement induced mixing of heavy, light, and split-off hole bands. Typical device responsivity at λ=10.8 μm is ∼0.04 A/W over the 20–77 K temperature range. A detectivity D*λ=3.3×109 cm √Hz/W was measured at a bias of −2.4 V for a temperature of 77 K at λ=10.8 μm and no cold shield. Room temperature FTIR measurements yield a quantum efficiency η≊3.1% at λp≊8 μm at 300 K.

A simple three-dimensional vapor phase model is used to interpret and clarify the selective area growth process. The model predicts both normal and anomalous profiles of thickness and composition, including long range effects. These are verified by an extensive set of experiments.

Heavy-and light-hole exciton transitions were observed from isolated quantum wells in two wafers of Alp 4Gao 6As/GaAs produced by molecular-beam epitaxy using interrupted growth at the heterointerfaces.The transitions can be assigned to well widths that are integral multiples of a GaAs monolayer width with the integers between 6 and 25. Direct measurements of the barrierlayer band gap and barrier-layer exciton binding energy were also made. A detailed envelopefunction analysis of this unique data set revealed the necessity of using a soft-edge potential well rather than a square well when analyzing such narrow wells. A reduction in exciton binding energies of 2.5 meV from free charge arising from unintentional barrier doping of -1X 10' cm ' was 0 found. Exciton binding energies for wells between 17 and 70 A are deduced from the analysis.

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