Growth of GaN on porous SiC and GaN substrates

Abstract

GaN films were grown on porous SiC and GaN templates using both plasma-assisted molecular beam epitaxy (PAMBE) and metal-organic chemical vapor deposition (MOCVD) to evaluate possible advantage of epitaxy on a porous substrate. For the growth of GaN on porous SiC by PAMBE, transmission electron microscopy (TEM) observations indicate that the exposed SiC suface pores tend to extend into the GaN film as open tubes and to trap Ga droplets. The GaN layers grown on porous templates have fewer threading dislocations originating at the interface, but they have additional defects in the form of half-loop dislocations which act to relieve the strain in the films. For PAMBE of GaN on porous GaN, dislocations existing in the porous seed layer are seen to propagate through the porous layer into the overgrown GaN, resulting in no dislocation reduction. For MOCVD of GaN on porous GaN, the initial regrowth tend to bend laterally the dislocations and enhance their annihilation, resulting in 5-10× fewer dislocations in the overgrown film.

HVPE GaN growth on porous SiC with closed surface porosity

“…Since the year 2000, there have been quite a number of reports on epitaxial growth of GaN on porous silicon carbide (PSC) substrates with various degrees of open porosity at the surface [6][7][8][9][10]. It has been demonstrated that GaN films grown on PSC were strain relaxed as compared to those grown on non-porous SiC.…”

High Optical Quality Nanoporous GaN Prepared by Photoelectrochemical Etching

“…[7][8][9] Although porous GaN offers a good alternate to grow high quality stress free over layer, yet very little work has been done. Recently, few studies on the bandgap and morphology control in porous GaN through electroless wet chemical and photoelectrochemical etching are reported.…”

Porous Silicon Carbide for MEMS

“…Many possible application scenarios, such as the layer transfer method or epitaxial growth of GaN [4], require the deposition of thin films via CVD without filling the porous material. This could in principle be shown with a sample having a resistivity of 0.106 Ω·cm, as is illustrated in Figure 3.…”