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Proceedings Paper

Photoreflectance studies of electronic transitions in quantum well structures under high presure
Author(s): Holakere R. Chandrasekhar; Meera Chandrasekhar
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Paper Abstract

Superlattices of alternating layers of semiconductors were first proposed1 in 1970, and since then a variety of structures have been grown. Their technological importance has spurred considerable experimental and theoretical work. The unique feature of quantum confinement of carriers has made possible unusual devices. By combining various semiconductors and alloys of ffl-V, 11-TV and group IV materials, unusual band lineups between neighboring layers have been obtained. Both lattice matched and strained layer structures have been grown. In this article we will focus on the electronic structure of the quantum well heterostructures under the external perturbation of hydrostatic pressure. Pressure has been used extensively to investigate materials in regions of phase space not otherwise accessib1. lu the study of quantum well structures, it has also been used to move band edges in a controlled fashion, and alter band lineups, allowing the determination of band offsets with an accuracy that was not possible without the use of pressure. As in bulk semiconductors, optical techniques provide powerful tools in studying the electronic states in quantum well heterostructures (QWH). Photoluminescence (PL) spectroscopy is only sensitive to spectral features associated with energy states close to the bottom of the well due to rapid thermalization of carriers. Photoluminescence excitation (PLE) is often limited by the availability of tunable lasers. Photoreflectance (PR), on the other hand, can provide a rich structure due to both symmetry allowed and forbidden transitions encompassing the entire quantum well. This sensitivity is due to the derivative nature of the spectroscopy. Experiments can be carried out easily at different temperatures and over wide spectral regions. This article is organized as follows. In section 2 we will review some of the theoretical calculations of electronic bands in quantum wells and discuss the changes expected under pressure. In Sec. 3, we discuss the experimental details, including descriptions of the optical techniques used. Section 4 will deal with studies of the quantized transitions in GaAs/GaixAlxAs and GaSb/A1Sb QWH under pressure,using PR and PL. The examples are illustrative of the comparative merits of the two techniques.

Paper Details

Date Published: 1 August 1990
PDF: 14 pages
Proc. SPIE 1286, Modulation Spectroscopy, (1 August 1990); doi: 10.1117/12.20849
Show Author Affiliations
Holakere R. Chandrasekhar, Univ. of Missouri/Columbia (United States)
Meera Chandrasekhar, Univ. of Missouri/Columbia (United States)


Published in SPIE Proceedings Vol. 1286:
Modulation Spectroscopy
Fred H. Pollak; Manuel Cardona; David E. Aspnes, Editor(s)

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