Physico-Chemical nanomaterials science

Optical spectroscopy of Fe impurity centers in GaN grown from Ga-Fe-N solution at high pressure and high temperature
Nikolenko A.1, В. Tsykaniuk В.1, Strelchuk V.1, Sadovyi B.2, Sadovyi P.2, Porowski S.2, Petrusha I.3, Turkevich V.3 and Grzegory I.2
1 V. Lashkaryov Institute of Semiconductor Physics NASU, pr. Nauky 41, 03028 Kyiv, Ukraine 
E-mail: nikolenko@isp.kiev.ua
2 Institute of High Pressure Physics PAS, Sokolowska str. 29/37, 01-142 Warsaw, Poland
3 V. Bakul Institute for Superhard Materials NASU, Avtozavodska str. 2, 04074 Kyiv, Ukraine

Crystallization of GaN from solution of N in Ga at high pressure and high temperature (HP-HT) is one of the known methods allowing for the growth of GaN crystals. However, low solubility of N in Ga limits its practical applications. One of the ways to increase the solubility of N is using of metals solvents, such as Fe, which leads to higher solubility of nitrogen. But in the latter case, Fe from solution is expected to incorporate into GaN affecting its physical properties. Therefore, investigation of Fe impurity centers and their influence on optical properties of GaN is important. We report on photoluminescence (PL) studies of GaN grown for the first time from Ga-Fe-N solution in HP-HT process at 1 GPa and 1500 °C [1].
PL spectra in the NIR range consist of two signals – intense peak at 1.193 eV and less intense feature at 1.298 eV with structured phonon sidebands on the low-energy side. The PL signal at ~1.193 eV is attributed to Ti2+ incorporated into the GaN. The PL band at 1.298 eV is attributed to ZPL of 4T1-6A1 internal 3d transition of Fe3+ center in GaN, whereas structured low-energy sideband – to its vibrational replicas. The micro-scale variations of intensity, shape, and position of Fe3+ ZPL peak along the GaN crystals are discussed in relation with non-uniform incorporation of Fe impurity and distortion of nitrogen tetrahedron due to defect complexes at high Fe concentrations. The described observations are in good agreement with the results of TOF-SIMS analysis.

1.	Sadovyi B., Sadovyi P., Petrusha I., Dziecielewski I., Porowski S., Turkevich V., Nikolenko A., Strelchuk V., Grzegory I. Physical properties of Ga-Fe-N system relevant for crystallization of GaN – initial studies // J. Cryst. Growth -2019. -507. -P. 77-86.