Preparation and lithium doping of gallium oxynitride by ammonia nitridation via a citrate precursor route
Gallium oxynitride, isostructural to hexagonal gallium nitride (h-GaN), was obtained by ammonia nitridation of a precursor prepared from the addition of citric acid to an aqueous solution of gallium nitrate. Gallium oxynitride produced at 750 °C had a small amount of gallium vacancies, and was formu...
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Published in | Journal of solid state chemistry Vol. 180; no. 7; pp. 1984 - 1989 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
San Diego, CA
Elsevier Inc
01.07.2007
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Gallium oxynitride, isostructural to hexagonal gallium nitride (h-GaN), was obtained by ammonia nitridation of a precursor prepared from the addition of citric acid to an aqueous solution of gallium nitrate. Gallium oxynitride produced at 750
°C had a small amount of gallium vacancies, and was formulated as (Ga
0.89□
0.11) (N
0.66O
0.34) where the symbol □ stands for gallium vacancy. Both the gallium vacancies and oxygen substituted for nitrogen were randomly distributed within the structure. The amount of vacancies decreased with nitridation temperatures in the range of 750–850
°C. Approximately, 10
at% Li
+ was doped into the gallium oxynitride, using a similar preparation with the additional presence of lithium nitrate, resulted in the random substitution of Ga
3+ in an atomic ratio of Li/Ga<1 at 750
°C. Oxygen was codoped with lithium and substituted nitrogen in the wurtzite-type crystal lattice. These substitutions reduced the electrical conductivity in the gallium oxynitride semiconductor. A new oxynitride, Li
2Ga
3NO
4, was also obtained with Li
2CN
2 impurity using similar preparations from a mixture of Li/Ga⩾1. The crystal structure was isostructural with h-GaN, and was refined as
P6
3
mc with
a=0.31674(1)
nm, and
c=0.50854(2)
nm. The Ga and Li occupancies at the 2
b site were refined to be 0.6085 and 0.3915, respectively, assuming that the other 2
b site was randomly occupied with 1/5O and 4/5N. When the new compound was washed for over 1
min for the removal of Li
2CN
2 impurities, it was decomposed to a mixture of
α-GaOOH and
α-LiGaO
2. The as-prepared product with Li/Ga=1 showed the highest intensity in yellow luminescence among the products under excitation at 254
nm.
Schematic gallium vacancy distribution within a Ga-plane in wurtzite-type gallium oxynitride prepared via a citrate precursor route. Closed and open circles represent gallium and its vacancy sites, respectively. This is the most probable case among various kinds of statistical vacancy distribution, where Ga/vacancy=6/1 in atomic ratio. About 10
at% Li
+ could be doped to the gallium oxynitride by substituting Ga
3+. Well-crystallized new oxynitride, Li
2Ga
3NO
4, isostructural with h-GaN, was also obtained in the preparation with Li/Ga⩾1. |
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ISSN: | 0022-4596 1095-726X |
DOI: | 10.1016/j.jssc.2007.04.011 |