Photo-enhanced dissociation of hydrogen-magnesium complexes in gallium nitride

• Published in: Physica. B, Condensed matter Vol. 273-274; pp. 54 - 57
• Main Authors: Kamiura, Y, Yamashita, Y, Nakamura, S
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.1999
• Subjects: GaN; Hydrogen; Magnesium; Photo-enhanced dissociation; Photo-enhanced dissociation; Magnesium; GaN; Hydrogen
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(99)00405-6

We have studied the effect of UV light illumination during thermal annealing on the electrical properties of Mg-doped GaN films grown on (0001) sapphire substrates by the two-flow MOCVD. We performed isochronal annealing up to 800°C for 1h in a nitrogen atmosphere with and without UV light illumination, and measured annealing-induced changes in resistivity, hole density and mobility at 25°C using the van der Pauw method. Under no illumination, annealing around 550°C caused resistivity and mobility to decrease and simultaneously hole density to increase. This is consistent with the commonly accepted model that the hydrogen passivation of Mg is caused by the formation of electrically inactive Mg–H complexes and thermal annealing dissociates the complexes to activate Mg. The illumination of UV light with a peak wavelength around 350nm greatly enhanced the dissociation of Mg–H complexes, reducing the temperature of resistivity reduction from 550°C to 450°C. These suggest that the dissociation of Mg–H complexes may be accelerated by the electronic excitation of the complexes and/or by the changes of their charge states. In view of application, such an effect may be useful to reduce the temperature of thermal annealing to make as-grown GaN films conductive.