Optical Detection Properties of Silicon-Germanium Quantum Well Structures

摘要

A study has been carried out on Si/SiGe multi quantum well structures todetermine their applicability as normal incidence infrared detectors in the spectral range of 2-12 micrometers. The research effort was primarily experimental, however, extensive calculations were performed to initially explain the experimental data and then used to design subsequent structures. Multiple quantum well structures grown on both Si001 and Si110 substrates via molecular beam epitaxy were studied by photoluminescence, absorption, and photoresponse measurements over a wide parameter space. Variables included quantum well depth and width, well doping, number of wells and growth temperature. Well widths were varied from 20A to 50A, Ge composition from 10% to 60%, boron doping from 1 x 10(exp 18) cm(exp -)3 to 8 x 10(exp 19) cm(exp -3), number of wells from 5 to 30 and growth temperature from 550 to 710 deg C. Calculations using k.p theory and the envelope function approximation were performed to determine the position of the bound states in the wells, the amount of band mixing and the transition strengths for bound-to-bound transitions for Si001/Si sub (1-x)Ge sub x, Si110/Si sub (1-x)Ge sub x and GaAs/AlGaAs quantum well structures. The Si110 structures have more allowed energy bands which are significantly mixed. A comparison was made between Si001/Si sub (1-x)Ge sub x, Si110/Si sub (1-x)Ge sub x and GaAs/AlGaAs quantum well structures designed to operate in the 8-12 micrometer region, and all three showed comparable momentum matrix elements.