Growth of Gan on Porous Sic Substrates by Plasma-Assisted Molecular Beam Epitaxy

Abstract

We have explored the growth of GaN on porous SiC substrates by plasma-assisted molecular beam epitaxy. The porous 4H-and 6H-SiC(0001) substrates used in this study contain 10 to 100-nm sized pores and a thin skin layer at the surface. This skin layer was partially removed prior to the growth by H-etching. Transmission electron microscopy (TEM) observations indicate that the epitaxial GaN growth initiates from the surface areas between pores, and the exposed surface pores tend to extend into GaN as open tubes and trap Ga droplets. Plan-view TEM observations indicate that the GaN layers grown on porous substrates contain fewer dislocations than layers grown on non-porous substrates by roughly a factor of two. The GaN layers grown on a porous SiC substrate were also found to be mechanically more relaxed than those grown on non-porous substrates; electron diffraction patterns indicate that the former are free of misfit strain or are even in tension after cooling to room temperature.

Growth of GaN on porous SiC and GaN substrates

“…Our early attempts at PAMBE of GaN on porous SiC were performed on substrates for which the skin layer had not been fully removed [2]. For the low surface pore density (<1 µm -2 ) of those samples, TEM observations indicate that the epitaxial GaN growth initiates primarily from surface areas between pores.…”

“…Porous SiC has recently been explored as a promising substrate to grow epitaxial SiC and GaN with reduced dislocation density [1][2]. Such porous materials are produced by anodizing n-type SiC in hydrofluoric acid under ultra-violet illumination [3].…”

Electronic states of chemically treated SiC surfaces

“…The surfaces of our samples are somewhat inhomogeneous, so that the spectra vary from location to location. To provide an overall view of the spectroscopy we acquire typically a grid of 10×10 spectra over an area of 20×20 nm 2 and we plot all the spectra together in a single graph, thus permitting a convenient view of the main features of the spectra [9].…”

“…In particular, as the voltage V is swept from some starting voltage 1 V to an ending voltage with opposite sign 2 V , the separation is changed according to…”

“…Porous SiC has proven to be a useful substrate material for homoepitaxial growth of SiC [1] and heteroepitaxial growth of GaN [2]. Porous SiC has also been found to be a promising material for use as a semi-permeable membrane in biophysics applications [3].…”