9504259 Mohney This Research Planning Grant focuses on studies to understand fundamental materials science aspects of thermally stable electrical contacts to group III nitrides, primarily Gallium Nitride (GaN). Thermodynamic calculations will be used, along with x-ray diffraction and electron probe microanalysis of bulk phase equilibria samples, to determine key features of the solid phase diagrams in the Metal-Ga-N systems. This investigation will aid in the selection of thermally stable contact materials. In addition, because of the high vapor pressure of N2 over GaN and the presumed role of N vacancies on the carrier concentration in GaN, the gas phase equilibria are expected to exert a greater influence on the thermal stability and electrical properties of contacts to GaN than they do for contacts to the other III-V semiconductors. Both novel and conventional methods to control the GaN point defect concentration and the contact/GaN barrier height will then be evaluated for their potential to engineer the electrical properties of those contacts that are already attractive from the standpoint of thermal stability. These methods will include attempts to manipulate the N vacancy concentration immediately beneath the contact/GaN interface to influence the n-type carrier concentration. The role of the work function of the contact material on the barrier height and subsequent performance of the contact will also be evaluated. %%% While this project will focus primarily on the development of electrical contacts to Gallium Nitride, it will also be of benefit for future design of contacts to other group III nitrides, and will contribute to a greater understanding of materials issues for these semiconductors. During the planning period of the project, at least two model systems will be selected to test ideas for controlling the electrical properties and stability of contacts to Gallium Nitride. The planning period will aid the PI in accomplishing enough prelimin ary work to show the promise of ideas or to modify them based on the data acquired. Thus, support during the planning period will aid the PI in preparing a more competitive full proposal. ***
