Surface and Overlayer Electronic Structure of Wide Band Gap Nitride Semiconductors

Trustees Of Boston University, Boston

Investigators

Abstract

This individual investigator award is to a young professor at Boston University for a project to study both the basic surface electronic structure of wide band gap nitride semiconductors, and the electronic structure of metal and non-metal overlayers on such nitrides. The specific goals of the program are to first study the surface electronic structure of nitride alloys; then to study the adsorption of simple gas molecules on well characterized nitride surfaces in order to understand their chemical reactivity, passivation, and properties of non-metal overlayers; and finally to study the reaction of metals with nitrides with the aim of understanding the growth, structure, and stability of contact overlayers. The electronic structure will be measured using two complimentary spectroscopies: angle resolved photoemission and inverse photoemission. This combination of spectroscopic techniques will provide a comprehensive understanding of the surface electronic and chemical properties of wide band gap nitride semiconductors. The project will educate postdoctoral research associates, graduate and undergraduate students in the physics of novel semiconductor materials, and the application of state of the art spectroscopic probes in their study. %%% An important new class of semiconductor based on nitrogen compounds is the focus of intense scrutiny due to their numerous potential applications in lasers and other optical devices that operate in the blue/UV portion of the spectrum. These materials, known as wide band gap nitride semiconductors, also hold the promise of being used in electronic devices operating at much higher temperatures than conventional materials. While many simple devices have been fabricated from these nitrides, there remains an acute lack of knowledge about their surface properties. It is of vital importance for the full commercial exploitation of these new semiconductors to understand their basic surface properties since the surface electronic structure controls many aspects of their chemical reactivity, their structural stability, and how other materials are bonded to the nitrides to form, for example, electrical contacts. This individual investigator award to a young professor at Boston University is for a project to study surface properties of these semiconductors using two probes: photoemission spectroscopy and inverse photoemission spectroscopy. These probes involve respectively the excitation of the electrons in the material by illumination with intense x-rays and measuring their response, or inserting electrons into the solid, and measuring emitted x-rays. This combination of spectroscopies will provide a comprehensive understanding of the surface electronic and chemical properties of wide band gap nitride semiconductors. The program will also educate postdoctoral research associates, graduate and undergraduate students in the physics of novel semiconductor materials, and the application of state of the art spectroscopic probes in their study. ***