Photoassisted Chemical Vapor Deposition for Packaging and Fabrication of Wide-Band Gap Semiconducting Devices

摘要

Major improvements have been made in the fabrication and in the performancecharacteristics of boron carbide-based, wide-band gap semiconductor devices. During this grant, working boron carbide transistors, tunnel junctions and homojunction diodes were fabricated. These transistors and diodes were the first carbide based devices of their type to be reported in either academic laboratories or in industry. Protocols for boron carbide substrate fabrication were optimized and the boron carbide thin films were deposited on a wide variety of substrates, including Si(111), aluminum, steel, gold, titanium and silver. PACVD (photoassisted chemical vapor deposition) methods using orthocarborane as a source molecule, were tailored to achieve band gaps of up to 4.0 eV with temperature stability to 250 C. The boron carbide material was successfully doped both n-type and p-type, and methods of tuning the band gap by inclusion of phosphorus-containg dimeric chloro-phospha-3-carborane allowed the band gap to be tuned reliably over the range of 0.7 to 2.4 eV by appropriate adjustment of feed gas. A novel class of CVD molecules, the metallocenes, were used for n-type doping. The sensitivity of these molecules to electron or photon beams have also allowed metal wires and other metal-metal containing features to be written with dimensions as small as 500 angstroms in resolution.