Optimization of the growth of GaN epitaxial layers in an indigenously developed MOVPE system
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Sådhanå (2020)45:249 https://doi.org/10.1007/s12046-020-01471-6
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Optimization of the growth of GaN epitaxial layers in an indigenously developed MOVPE system ABHISHEK CHATTERJEE1,3 , V K AGNIHOTRI1, R KUMAR1,3, S PORWAL1, A KHAKHA1, G JAYAPRAKASH1, TAPAS GANGULI2,3 and T K SHARMA1,3,* 1
Semiconductor Materials Laboratory, Materials Science Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India 2 Synchrotons Utilization Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, India 3 Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094, India e-mail: [email protected]; [email protected] MS received 12 February 2019; revised 3 May 2020; accepted 15 July 2020 Abstract. Growth of GaN epitaxial layers is optimized in an indigenously developed nitride metal organic vapour phase epitaxy (MOVPE) system. The motivation of present work is to develop a simple MOVPE reactor which is though affordable but can deliver GaN epilayers of desired quality. The design and fabrication methodology of nitride MOVPE system is briefly discussed. MOVPE growth of GaN epilayers is carried out through a two-step growth process where influence of the growth parameters of low temperature buffer layer on the crystalline properties of high temperature GaN epilayer is discussed in detail. Optimum values of the growth temperature, annealing duration and thickness of GaN buffer layer are achieved. High resolution X-ray diffraction measurements (HRXRD) confirmed that the crystalline quality of GaN epitaxial layers is reasonable. A good surface morphology of the optimized sample is strongly corroborated by the results obtained from photoluminescence (PL) and HRXRD techniques. Usefulness of a systematic Williamson-Hall analysis in the optimization of growth of GaN epitaxial layers is demonstrated where a high value of lateral coherence length of GaN buffer layer is found to be a key parameter. Such an optimization process leads to the good crystalline quality of GaN epitaxial layers with low dislocation density. It is found that the high temperature GaN epilayers grown on the optimized GaN buffer layer are compressively stressed which is also revealed by the PL measurements. Keywords.
MOVPE; GaN; buffer layer; HRXRD; PL.
1. Introduction Considerable progress in the research and development of Gallium nitride (GaN) and its related ternary alloys involving Al and In is mainly driven by the improvement in the crystalline quality of nitride epitaxial layers. Nitride epitaxial layers are essential for the realization of high performance optoelectronic devices and are grown either by metalorganic vapour phase epitaxy (MOVPE) or molecular beam epitaxy (MBE) technique [1–5]. One of the major challenges in the growth of high quality GaN is related with the lack of suitable lattice matched substrate. In view of this, GaN epitaxial layers are usually grown on various foreign substrates like Si, SiC and Sapphire etc. [6–8]. Recently nat
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