Material Engineering of Novel Semiconductor Structures.
Abstract
The first experiments were done in the visible region of the spectrum, using familiar nonlinear material ZnSe in order to acquire experience in nonlinear spectroscopy. Highly sensitive measurements of the spectrum of nonlinear refractive index of ZnSe were done using the method of self-bending. This method, has shown significant advantage over conventional Kramers-Kronig method. The results of the measurements were somewhat unexpected, since the nonlinear index of refraction, n2 measured by us turned out to be quite large (10 to the -8th power sq. cm./W) and hard to explain using conventional wisdom of the thermally-induced bandgap shrinking. Therefore, we conducted additional set of measurements that gave the proof of the excitonic origin of the nonlinearity. After the near-infrared laser became fully operational, the main thrust was in the direction of investigation of nonlinear optical and electro- optical properties of the asymmetric coupled QW's. Efforts to locate reliable sources of MBE-grown QW material had finally succeeded. First experiments on photoluminescence and photoconductivity spectroscopy of asymmetric coupled QW's started. The samples used had 25 coupled QW periods each consisting of two Al<0. 357 Ga <0.65> As QW's, with thickness of 18A and 32A separated by 15A GaAs barrier. Thicker 100 A barriers separated the coupled QW's from each other. The entire undoped multiple QW structure was sandwiched between n and p Al<0.35 Ga <0.65> As layers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 30, 1990
- Accession Number
- ADA235014
Entities
People
- J. Khurgin
Organizations
- Johns Hopkins University