Ming Luo

Date of Graduation

2006

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Nancy C. Giles

Committee Co-Chair

Larry E. Haliburton

Committee Member

Larry A. Hornak

Committee Member

David Lederman

Committee Member

Thomas H. Myers

Abstract

II-VI semiconductors doped with transitional-metal (TM) ions have received much research interest for applications such as broadly tunable mid-infrared lasers and saturable absorber for 1.5 μm eyesafe lasers. In this work, several characterization techniques including absorption, photoluminescence (PL), time-resolved photoluminescence (TRPL) and electron paramagnetic resonance (EPR) were applied to study some TM-ion-doped samples. These samples include a set of Cr-doped ZnTe epilayers prepared by the molecular-beam epitaxy technique (MBE) and seven bulk polycrystalline ZnSe samples doped with Fe and/or Co. The PL study in the visible region applied on the set of Cr-doped ZnTe film samples revealed the possible contaminants (e.g., arsenic, sodium and oxygen) in these samples. The infrared PL and lifetime results indicated that the ZnTe:Cr films grown at WVU are comparable in optical behaviors to the bulk samples. By monitoring the Cr2+-2μm emission, the optimum doping and growth parameters were determined to be [Cr]: mid-1018cm -3 and a Zn/Te beam equivalent pressure (BEP) ratio of 0.8. The optical investigations and EPR study applied on the polycrystalline bulk samples showed that divalent TM ions (Co2+ and Fe 2+) were successfully incorporated into the window-grade ZnSe materials, thus it is possible to prepare TM-ion-doped ZnSe samples with optical behaviors similar to that of single crystals by diffusion anneals. A detailed study on a ZnSe sample intentionally codoped with Fe and Co revealed the nonradiative energy transfer between Co2+ and Fe2+. This is the first clear report of energy transfer associated with divalent TM ions in II-VI semiconductors.

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