Date of Award

7-1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Robert L. Hengehold, PhD

Second Advisor

Yung Kee Yeo, PhD

Abstract

In recent years, there has been interest in obtaining efficient photoluminescence (PL) and electroluminescence from Si1-xGex/Si or Si/Ge superlattices. In this dissertation, longperiod c/Si superlattices grown by molecular beam epitaxy at 500°C and annealed post-growth using rapid thermal annealing were investigated using photoluminescence (PL). The as-grown samples have broad PL bands from isoelectronic centers related to Ge complexes as well as sharp near-edge bound exciton lines. The broad PL band was found to be 120 meV below the band gap, after accounting for the effects of confinement of holes. Post-growth annealing resulted in a reduction in the broad PL band activation energies and a shift of the broad band to higher energies. The reduction in the activation energies of the broad band were found to be due to the position of the emission centers within the Si1-xGex layers. The emission centers in the middle of the Si1-xGex were deactivated at higher temperatures than those at the edges, which caused the shift of the broad band to lower energies as the sample temperature increased. The shifts of the broad PL band as the annealing temperature increased were found to be due to a net shift of the emission centers towards the interfaces. The effective local band gap at the interfaces was higher than the average in the Si1-xGex layers, thus resulting in the shift of the broad PL band to higher energies for the annealed samples.

AFIT Designator

AFIT-DS-ENP-92-002

DTIC Accession Number

ADA256467

Comments

The author's Vita page is omitted.

Plain-text title form: Photoluminescence Study of Si1-xGex/Si and Si/Ge Strained Layer Superlattices

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