Vacancy defects in bulk ammonothermal GaN crystals |
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Authors: | F Tuomisto J-M Mäki M Zaj?c |
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Institution: | 1. Department of Applied Physics, Aalto University, P.O. Box 11100, FI-00076 Aalto Espoo, Finland;2. Ammono Sp. z o. o., Czerwonego Krzy?a 2/31, 00-377 Warsaw, Poland |
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Abstract: | We have applied positron annihilation spectroscopy to study in-grown vacancy defects in bulk GaN crystals grown by the ammonothermal method. We observe a high concentration of Ga vacancy related defects in n-type samples in spite of the low growth temperature, suggesting that oxygen impurities promote the formation of vacancies also through other mechanisms than a mere reduction of thermodynamical formation enthalpy. On the other hand, no positron trapping at vacancy defects is observed in Mg-doped p-type samples, as expected when the Fermi level is close to the valence band and intrinsic defects are dominantly positively charged. Annealing of the samples at temperatures well above the growth temperature is found to change significantly the defect structure of the material. |
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Keywords: | A1 Characterization A1 Defects A2 Single crystal growth B1 Nitrides B2 Semiconducting III&ndash V materials |
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