Acquistion of Instrumentation for Stress Effects on the Electrical Properties of Group III-Nitride Modulation Doped Heterostructures

Virginia Commonwealth University, Richmond VA

Investigators

Abstract

A Helium gas hydrostatic pressure apparatus with electrical and optical access and a Kulicke and Soffa wire bonder will be acquired to investigate piezoelectric constants in III-nitrides. The bonder is needed to attach metallic wires for electrical access to the semiconductor for conductance measurements. This instrumentation will nicely complement our existing effort funded by NSF, which deals specifically with the polarization issues in nitrides. The effort will be supported by our strong in house nitride growth effort with MBE and MOCVD. Prof. Nathan of the University of Minnesota, with whom we will collaborate, has already conducted these sorts of experiments in nitrides. Initial experiments of resistivity vs. stress on un-gated Hall bars have already been conducted. The resistivity exhibits slow long term drifts (time constants of order 100 to 1000 seconds. Similar effects observed earlier in GaAs have been ascribed to a defect center associated with shallow donors called the DX center. However, the effect in GaN is more complex, but it is reminiscent of the type of persistent photoconductivity observed in GaAs in the early stages of development. Clearly trapping effects will have to be separated from the piezoelectric effects. Such a study is crucial to the practical application electronic nitride devices. The requested instrument consists of 1. Helium gas hydrostatic pressure apparatus with electrical and optical access, which will be purchased from Unipress, Poland. ($121,749) Wire bonder which will be purchased from Kulicke & Soffa (model 4524 - $20,092.50) Hadis Morkoc Virginia Commonwealth University Department of Electrical Engineering and Physics Department 601 W. Main Street P. O. Box 843072 Richmond, VA 23284-3072