Hydride vapor phase epitaxy HVPE

Currently, the available single crystal GaN substrates are limited by the size and point defects that make them unsuitable for mass production [1]. An alternative to native GAN substrates is to use free-standing GaN templates prepared by hydride vapor phase epitaxy (HVPE), which has a typical thread dislocation (TD) density of 105-106 cm-2, however, the high price limits their availability [2],... 

In this chapter, various aspects of the growth of GaN films on porous SiC (PSC) by hydride vapor phase epitaxy (HVPE) are discussed (here, we understand that a porous SiC substrate is a SiC wafer with a several micrometer-thick porous layer in it). First, the preparation of PSC substrates under various conditions, and the properties of the PSC fabricated are described. Next, mechanisms of formation of different types of PSC structure and the stability of porous substrates under thermal and plasma treatment are considered. The final part of the chapter treats GaN epitaxial growth, film properties, and explanations for improved epitaxy provided by porous substrates. 

For commercially available samples, the major fabrication method is hydride vapor phase epitaxy (HVPE). In the HVPE method, GaCl and NH3 react to produce GaN, with H2 and HCl gases as by-products GaCl + NH3 —) GaN + H2 + HCl (Maruska Tietjen, 1969) (Fig. 3). 

While considerable progress was made in thin-fihn growth of nonpolar GaN from 2000-2002, thick-film or bulk growth of nonpolar orientations continued to be elusive until late 2002. The performance of nonpolar GaN-based devices would be limited by the lack of low-defect density film and substrate options. This chapter describes the progress achieved in thick-film nonpolar GaN growth via hydride vapor phase epitaxy (HVPE) toward the goal of producing low-defect density nonpolar GaN thick-films and substrates. 

Although first deposition experiments of nonpolar GaN films on r-plane sapphire were performed as early as in 1987 [5], the defect structure in wurtzite GaN and related compounds has been mainly studied in the past focusing on films oriented along the hexagonal [0001] axis (c-axis). Growth techniques such as molecular beam epitaxy (MBE) [1], metal organic vapor phase epitaxy (MOVPE) [6], and hydride vapor phase epitaxy (HVPE) [7,8] are established for polar as well as nonpolar GaN growth. The structural quality of a-plane GaN... 

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