Investigation and Mitigation of the Electrical Effects of Crystal Defects on SiC and GaN Devices

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This project will investigate the performance-limiting effects of crystal defects on the electrical properties of p-n and Schottky diode junctions made in two important wide-gap semiconductor materials, silicon carbide (SiC) and gallium nitride (GaN). These materials are both currently of great interest for high power, high temperature, high frequency electronic applications. GaN is also of interest for short wavelength optoelectronic applications. A major problem in these new materials is the effects of crystal defects on breakdown voltage, leakage currents, and other nonidealities of devices fabricated from them. The objective is therefore to systematically study the effects of various defect classes on electrical properties of junctions in each material, so that the most important defects can be identified and targeted for elimination. The defects will be studied using current-voltage and capacitance-voltage measurements, deep level transient spectroscopy (DLTS), electron beam induced current (EBIC) imaging, electroluminescence under forward and reverse bias, and thermal imaging. The nature of the crystalline defects will be determined using synchrotron white-beam X-ray topography (SWBXT), optical microscopy & selective etching, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy (TEM). Very small devices containing at most one defect will be studied to isolate the effects of specific defect types. Several methods of passivating the effects of defects will also be investigated. Industrial collaborations are planned with Motorola and Epitronics. A Ph.D. student will be educated, and information on wide gap materials and devices will be made widely available to other universities and the general public over the Internet.