Date of Award

5-2002

Document Type

Thesis

Degree Name

Master of Science in Materials Science and Engineering (MSMSE)

Department

Materials Science

First Advisor

Dr.Nacir Tit

Second Advisor

Prof. Dr.Radhi AI-Jishi

Third Advisor

Dr.Mohammed Elzain

Abstract

Semiconductors are distinguished among all materials by having a non-vanishing energy band gaps. They are often used in industry in the form of alloys or heterostructures in order to tailor energy gaps suitable for the desired applications. In general, semiconductor materials have broad applications in industry, ranging from micro-electronic devices, to light emitters and detectors, to laser and solar cells. In the last two decades, particular attention has been given to the II-VI semiconductor heterostructures because of their suitability as photoelectronic devices covering from the infra-red to the ultra-violet spectral ranges. The scope of this thesis belongs to the field of band gap engineering and deals with an investigation of the main parameters directly affecting the electronic band structures and optical properties of the strained CdTe/ZnTe(001) superlattices (SLs). As many other common-anion heterostructures, the valence-band offset (VBO) is also finitely small for these SLs. This fact makes both the biaxial strain and the spin-orbit coupling important parameters in controlling the SL character because they affect the level splitting of the valence-band top states. For this reason, we have used in our computation the Sp3s* tight-binding method with inclusion of strain and spin-orbit effects. We have calculated the band structures, densities of states, and oscillator strengths versus SL layer thicknesses, biaxial strain state, and VBO. Our results show that the electron is always localized within CdTe slabs whereas the hole behavior controls the SL character. Our results are further compared to photoluminescence experiments and shown to be consistent with the strain morphology and structural and optical properties of the experimental samples.

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