Doctor of Philosophy, The Ohio State University, 2009, Electrical and Computer Engineering

The use of step-graded SiGe buffers to accommodate the lattice constant difference between Si and III-V materials is an extremely promising approach to achieve monolithically integrated III-V optoelectronic device technology on Si wafers. The potential of this technology has already been demonstrated by the integration of numerous high performance GaAs-InGaP based devices on Si substrates. As a result, there is now a great interest in knowing the basic properties of residual defects within the III-V/SiGe materials and devices since their understanding is fundamental to maintain the progress achieved to date. The focus of this research if to investigate “grown in” defects present within GaAs and InGaP-based layers and devices grown on SiGe/Si generating a fundamental understanding on defect introduction in lattice mismatch III-V/SiGe heteroepitaxy. The role of the SiGe substrate is analyzed by comparing deep level properties with identical structures grown on GaAs substrates. Results showed that the presence of dislocations do not introduced additional deep levels. In addition, and from the point of view of the technology, the effect of radiation damage in III-V/SiGe PV structures is analyzed, specifically detection and identification of “ambient-generated” defects that result from the application of these materials and photovoltaic devices operating in the space environment. In this dissertation the first radiation study for III-V/SiGe structures was performed. Results indicated that for single junction GaAs structures, the primary impact of the SiGe/Si substrate was to improve the radiation-tolerance of these devices, in particular for n+p GaAs diodes. While DLTS results showed generally lower radiation-induced trap concentrations for both n-type and p-type GaAs grown on SiGe compared to growth on conventional substrates, the reduction was far more dramatic for p-type GaAs. The improved radiation-tolerance for GaAs grown on SiGe/Si is attributed to interactions bet (open full item for complete abstract)

Committee: Steven Ringel A (Advisor); Wu Lu (Other); George Valco J (Other); Dennis Guenther A (Other) Subjects: Materials Science