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.

2010

• 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).

2009

• Identification and carrier dynamics of the dominant lifetime limiting defect in n(-) 4H-SiC epitaxial layers Phys. Status Solidi A: Applications and Materials Science 206, 2257-2272 (Oct 2009)
• Cathodoluminescence studies of the inhomogeneities in Sn-doped Ga₂O₃ nanowires, Nano Letters 9 (2009) 3245.
• Cathodolumiensce study of the properties of stacking faults in 4H-SiC homoepitaxial layers, Appl. Phys. Lett. 94 (2009) 092101.

2008

• Carrier Lifetime Measurements in n 4H-SiC Epilayers, J Appl Phys 103 033702 (2008).
• Semi-insulating GaN substrates for high-frequency device fabrication, J. Crystal Growth 310, 3968 (2008).
• AIN bandgap temperature dependence from its optical properties, Journal of Crystal Growth 310, 4007 (2008).

2007

• Compensation Mechanism in High Purity Semi-Insulating 4H-SiC, J. Appl. Phys. 101, 053716 (2007).
• Properties of epitaxial GaN on refractory metal substrates, Appl. Phys. Lett. 90, 091910 (2007).
• Rare-earth chloride seeded growth of GaN nano- and micro-crystals, Appl. Surf. Sci. 253, 6157 (2007).
• Optical and Magnetic Resonance Studies of Mg-doped GaN Homoepitaxial Layers Grown by Molecular Beam Epitaxy, Physica B 401-402, 327 (2007).

2006

• Lifetime limiting defects in n-4H-SiC epilayers, Appl. Phys. Lett. 88, 052110 (2006).
• Annealing of Multivacancy Defects in 4H-SiC, Phys. Rev. B 74, 235201 (2006).

2005

• Estimation of Residual Nitrogen Concentration in Semi-Insulating 4H-SiC Substrates via Low Temperature Photoluminescence, Appl. Phys. Lett. 86, 052109 (2005).

2003

• Photoionization Spectroscopy of deep defects responsible for current collapse in nitride-based FETs, J. Phys.: Cond. Matter 15, R1641-R1667 (2003).

"Material contained herein is made available for the purpose of peer review and discussion and does not necessarily reflect the views of the Department of the Navy or the Department of Defense."