Wisconsin Alumni Research Foundation

Semiconductors & Integrated Circuits
Semiconductors Integrated Circuits
WARF: P230402US01

Inventors: Chirag Gupta, Swarnav Mukhopadhyay, Shubhra Pasayat

There is growing interest in gallium nitride (GaN) as a material for high-frequency and high-power applications, such as high electron mobility transistors (HEMTs) and other field effect transistors (FETs), due to its large band gap and high internal breakdown field. Unfortunately, GaN layers grown by current methods, such as metalorganic vapor phase epitaxy (MOVPE), result in dislocations and donor-like-impurities, such as residual oxygen or nitrogen vacancies, which cause n-type conductivity in unintentionally doped GaN.
The Invention
UW-Madison researchers have developed methods for creating semi-insulating N polar GaN using carbon (C) and iron (Fe)-doping, and related structures for semi-insulating N-polar GaN templates. Propane incorporation in N-polar GaN is difficult due to the high temperature growth conditions. The researchers optimized the growth conditions and parameters to maximize propane incorporation, and the propane doped N-polar GaN shows semi-insulating behavior and device quality material properties even with very high propane doping. This achieves good incorporation efficiency with fully semi-insulating behavior and good material quality.

For Fe-doped N-polar GaN, controlling the turn-on and turn-off of Fe-doping is a huge challenge in III-nitride materials and it affects the device performance massively, causing dispersion, change of threshold voltage, unintentional compensation of n-type dopants etc. The inventors now have a two-step method of obtaining semi-insulating N-polar GaN layer using Fe-doping to produce high quality material with high resistivity. Sluggish turn on and turn off effect of Fe-doping is successfully tuned using optimized growth conditions.
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