Solid State and Optics Seminar

Wednesday, February 15, 2006

1:00 p.m.

107 Mason Lab

"Tailoring the Nanometer-Scale Structure and Properties of Dilute Semiconductor Alloys"

Prof. Rachel S. Goldman
Dept. of Materials Science and Engineering
University of Michigan

Abstract

For many compound semiconductors, the introduction of impurities at dilute concentrations leads to dramatic changes in the electronic, optical, and magnetic properties. For example, the introduction of a few percent nitrogen into GaAs leads to a band gap reduction of hundreds of meV. Furthermore, the incorporation of a few percent manganese into GaAs enables a combination of semiconducting and ferromagnetic behavior. The resulting narrow gap nitride and dilute magnetic semiconductors are promising for several applications ranging from long-wavelength light-emitters and high efficiency solar cells to spin-electronics and spin-optoelectronics. In both cases, the nanometer-scale details of impurity incorporation are critical to understanding and controlling the observed properties. In this talk, I will discuss our investigations of the growth, nanometer-scale structure, and properties of dilute GaAsN and GaMnAs alloys, using nuclear reaction analysis and cross-sectional scanning tunneling microscopy, in conjunction with several other measurements. In the case of GaAsN, I will discuss the incorporation of N into substitutional vs. interstitial lattice sites [1], and its effect on electron transport and optical properties. In the case of GaMnAs, I will discuss clustering of MnGa and AsGa point defects [2], and its possible effect on electronic and magnetic properties.

[1] M. Reason, H.A. McKay, W. Ye, R.S. Goldman, et al, APL 85, 1692 (2004).
[2] J.N. Gleason, M.E. Hjelmstad, V.D. Dasika, R.S. Goldman, et al APL 86, 011911 (2005).

This work is supported in part by DOE, NSF, AFOSR, ONR, TRW, and NASA-Lewis.

Host: Mark Reed