IV-VI semiconductor structures for laser fabrication of silicon.

Abstract

This dissertation describes experiments undertaken to develop techniques required to develop IV-VI lasers grown on silicon. A review of the IV-VI materials system, diode laser structures, recent IV-VI laser results, epitaxial growth techniques, and thermal modeling results introduces the reader to the structures and materials to be discussed. Designs for three different IV-VI laser structures on silicon follow. Three types of experimental structures are investigated next: those grown on BaF$\sb2$ substrates by liquid phase epitaxy (LPE), those grown on silicon by molecular phase epitaxy (MBE), and those grown on silicon by a combination of MBE and LPE. The author's recommendations for future work sum up the body of the text. Five appendices are included to document procedures (BaF$\sb2$ chemical mechanical polishing and IV-VI material preparation for LPE), to provide supplementary material (cleaving jig preparation for epitaxial lift-off of IV-VI layers and the effects of oxygen adsorption upon IV-VI materials), and to act as a repository for program code generated during this project (six programs and their supporting code for acquiring, displaying, and converting measurement data).

Fabrication of commercially competitive IV-VI tunable diode lasers has been hampered by lack of suitable substrates. Lasers grown on IV-VI materials themselves are acceptable for low temperature operation, but poor substrate thermal conductivity limits their operation to the cryogenic regime. An alternative substrate material, BaF$\sb2, $ is a promising alternative, but available substrates are often of questionable crystalline quality. High quality silicon, however, is readily available and may be used to grow epitaxial BaF$\sb2.$ This BaF$\sb2$ epilayer may then be used as a substrate for further growth of IV-VI diode lasers. In addition, the water solubility of BaF$\sb2$ permits lift-off of the laser structures and remounting on a more electrically and thermally accommodating substrate--such as copper.