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Growth of Ga2 O3 by furnace oxidation of GaN studied by perturbed angular correlations Michael Steffens1,2 · Reiner Vianden2 · Alberto F. Pasquevich3,4

© Springer International Publishing Switzerland 2016

Abstract Ga2 O3 is a promising material for use in “solar-blind” UV-detectors which can be produced efficiently by oxidation of GaN. In this study we focus on the evolution of the oxide layer when GaN is heated in air. The experimental method applied is the perturbed angular correlation (PAC) spectroscopy of γ -rays emitted by radioactive nuclides, here 111 Cd and 181 Ta, whose parent nuclei are ion implanted into films of GaN grown on sapphire. As the emission pattern for nuclei in GaN is clearly distinct from that of nuclei in Ga2 O3 , the fraction of probe nuclei in the oxide layer can be directly measured and allows to follow the time dependent growth of the oxide on a scale of less than 100 nm. Additional measurements were carried out with the oxidized sample held at fixed temperatures in the temperature range from 19 K to 973 K showing transitions between the hyperfine interactions of 111 Cd in the oxide matrix both at high and low temperatures. A model for these transitions is proposed. Keywords Perturbed angular correlation spectroscopy · TDPAC · Gallium nitride · Gallium oxide · Self-trapped hole · Furnace oxidation This article is part of the Topical Collection on Proceedings of the International Conference on Hyperfine Interactions and their Applications (HYPERFINE 2016), Leuven, Belgium, 3-8 July 2016  Michael Steffens

[email protected] 1

Fraunhofer Institute for Technological Trend Analysis INT, Appelsgarten 2, 53879 Euskirchen, Germany

2

Helmholtz - Institut f¨ur Strahlen- und Kernphysik der Universit¨at Bonn, Nussallee 14-16, 53115 Bonn, Germany

3

Departamento de F´ısica, IFLP, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La Plata, Argentina

4

Comisi´on de Investigaciones Cient´ıficas de la Provincia de Buenos Aires, La Plata, Argentina

117

Hyperfine Interact (2016) 237:117

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1 Introduction Ga2 O3 is a transparent wide band gap semiconductor which can be used for high-efficiency, “solar blind” UV photodetectors. However, the controlled production of high quality films of monoclinic β-Ga2 O3 which are essential for the fabrication of such detectors is still difficult. In a recent study Weng et. al. [1] presents a feasible and efficient way to grow Ga2 O3 by furnace oxidation of GaN. This is an important step forward since thermal oxidation is a simple, cheap and clean process. In this study we focus on the details of the evolution of the oxide layer when oxidized at 1223 K in dry air. The experimental method applied is the perturbed angular correlation (PAC) technique of γ -rays emitted by probe nuclides, here 111 In and 181 Hf, which are ion implanted into the GaN samples [2]. It allows to measure the electric field gradient (EFG) at the crystal site of the probe nuclei. Since the EFG for nuclei in GaN is clearly distinct from that