Date of Award

10-18-1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Robert L. Hengehold, PhD

Abstract

A study has been carried out on Si/SiGe multi quantum well structures to determine 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 Si[001] and Si[110] 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 20Å to 50Å, Ge composition from 10% to 60%, boron doping from 1 x 1018 cm-3 to 8 x 1019 cm-3, number of wells from 5 to 30 and growth temperature from 550 to 710 °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 Si[001]/Si1-xGe sub x, Si[110]/Si1-xGex and GaAs/AlGaAs quantum well structures. The Si[110] structures have more allowed energy bands which are significantly mixed. A comparison was made between Si[001]/Si1-xGex, Si[110]/Si1-xGex and GaAs/AlGaAs quantum well structures designed to operate in the 8-12 µm region, and all three showed comparable momentum matrix elements.

AFIT Designator

AFIT-DS-ENP-96-07

DTIC Accession Number

ADA325106

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