Wide Bandgap Materials
Wide bandgap semiconductors are of particular interest to the Navy because of their capability of operating at high power, high temperature and/or high frequency levels that far exceed the capabilities of Si-based technology. The development of high-voltage switching devices employing SiC is actively being pursued, while III-Nitride materials enable the fabrication of high-frequency, high output power microwave devices. Currently, the ability to integrate such devices into Navy systems is limited by device degradation due to material defects. Research is directed toward characterizing both point and extended defects in these systems, identifying those defects that limit device performance and understanding the microscopic mechanisms that lead to device degradation.
These studies are carried out in close connection to material growth facilities within the Laboratory and with outside commercial and academic institutions. Defects are investigated using several contactless optical probes, including steady-state and time-resolved photoluminescence, Raman spectroscopy and cathodo-luminescence, as well as magnetic resonance techniques and secondary electron and atomic force microscopy. Recent studies have focused on defects responsible for semi-insulating behavior and reduced minority carrier lifetimes in 4H-SiC, impurities associates with n-type conductivity in the nitrides and defects limiting nitride-based FET performance.
- Recombination processes controlling the carrier lifetime in n(-)4H-SiC epilayers with low Z(1/2) concentrations, Journal of Applied Physics 108, 033713 (Aug 2010).
- Effect of threading screw and edge dislocations on transport properties of 4H-SiC homoepitaxial layers, J. Appl. Phys. 108, 013708 (2010).
- Thick homoepitaxial GaN with low carrier concentration for high blocking voltage, J. Crystal Growth 312, 2616 (2010)
- Properties of the state-of-the-art of bulk III-V Nitrides substrates and homoepitaxial layers, J. of Physics D: Appl. Phys. 43, 073001 (2010).
- Optical probing of low-pressure solution grown GaN crystal properties, J. Crystal Growth 312, 2564 (2010).
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