关键词: GaN, 异质外延, HVPE

Abstract: A new growth control way, Function Control Method, is introduced in GaN heteroepitaxy by hydride vapor phase epitaxy (HVPE). Function Control Method is a growth control way in which growth parameters vary as certain mathematical functions of time. Two growth schemes are designed by the aid of this method to solve two main problems confronted in obtaining free-standing GaN substrates by HVPE. In the heteroepitaxial growth scheme of crack-free high-quality thick film, growth parameters’ variations as gradual functions of time ensure that the growing of high-quality GaN maintains sustainable advantage while the strain is being released gradually. Besides, the periodic functions turn the problem of thick-film heteroepitaxy into an easy one of thin-film heteroepitaxy. In the separation scheme of the thick epilayer, growth parameters’ twice sharp transitions produce a weakly connected thin interlayer. Also, except for the twice sharp transitions, growth parameters’ variations as gradual functions of time bring about stress difference between two sides of the weakly connected thin interlayer. The stress difference can be further intensified during the cooling process, leading to the thick epilayer’s self-separation at the weakly connected thin interlayer. With the combination of the two schemes, 1 mm-thick transparent GaN crystal with a smooth surface was obtained, which proved the effectiveness of Function Control Method. Relying on growth parameters’ regular orderly change over time, this method develops new ways of material growth control, and links properties of the growing material with the mathematical functions according to which growth parameters vary.

Key words: GaN, heteroepitaxy, HVPE