Growth of high-quality large GaN crystal by Na flux LPE method

Abstract

ABSTRACT We have been developing the technology that enables us to grow high quality and large GaN single crystals for producing high quality GaN single crystal su bstrates using Na flux method. In 2 005, we have succeeded in the growth of 2-inch GaN substrates with low dislocation density (< 10 5 cm -2 ) by applying the Liquid Phase Epitaxy to the Na flux method. Recently, we reported that dislocati on density lower than the order of 10 4 cm -2 and the growth rate more than 20 um/h is achievable in the Na flux LPE. This achievement was due to introducing some new techniques; such as thermal convection, mechanical stirring, addition of carbon additive, development of new growth apparatus and so on, to the Na flux LPE. Keywords: GaN, Single crystal, Substrate, Na flux, LPE INTRODUCTION Some approaches such as the hydride vapor phase epitaxy (HVPE) [1-3], ammonothermal growth [4-6], high-pressure solution growth [7-9], and the Na flux [10-25] meth ods have been found to enable the growth of large and high-quality GaN single crystals. The realization of high-quality GaN single crystal substrates with large diameter is expected to bring about the next generation of highly efficient electronic devices. Although 2-inch GaN substrates synthesized by the HVPE method have already been commercially produced, the curvature and large dislocation density included in the crystal have been identified as serious problems for use in future devices. In contrast, the other solution growth methods mentioned above have achieved the growth of GaN crystals with low dislocation density. The high-pressure solution growth method initially demonstrated extremely low dislocation GaN crystals. In the Na flux method, significant reduction of dislocation density was confirmed by applying the liquid phase epitaxy (LPE) technique [22]. Most recently, ammonothermal growth, which has been considered as a disadvantageous method from the perspective of dislocation density, has achieved dislocation density on the order of 10