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High pressure annealing method for modification of structural, optical and electrical properties of Group-II nitride semiconductor structures.

High pressure has proven to be an important tool in nitride technology and research. At atmospheric pressure GaN decomposes at temperatures lower than 1000-1100oC.

High pressure of nitrogen up to 15kbar (1.5GPa) makes it possible to extend the accessible temperature range up to about 1500oC. Such temperatures are required for an efficient growth of GaN single crystals from the N-solution in liquid gallium, as well as for making the defects/impurities mobile (diffusion, defect annihilation, etc.), what is necessary, for example, for efficient removal of implantation defects
Specially designed high pressure chamber has been tested by the UNIPRESS team.

We have used undoped heteroepitaxial layers of GaN on sapphire applying high pressure annealing in nitrogen gas and in the pressure range of 10-16kbar, temperatures 1000 - 1500oC. We have found and improvement of the structural and optical properties of the used layers at some regions of temperatures and pressures.

Particularly, Full Width at Half Maximum (FWHM) of the Xray reflections decreases by factor of 30% at pressures P=13-14kbar and T=1300oC-1400oC.

Photoluminescence intensity (of donor-bound-exciton) can increase by factor 3-4 .

The above obtained results reflect very likely a decrease in the concentration of threading dislocations in GaN/sapphire. It demonstrates the potential of the method for use in other technology related activity. In particular, annihilation of implantation defects and doping.

Reported by

UNIPRESS, Instytut Wysokich Cisnien, Polskiej Akademii Nauk,
Ul. Sokolowska, 29
01-142 Warszawa
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