Role of TiN Film in the Fabrication of Freestanding GaN Wafers Using Hydride Vapor Phase Epitaxy with Void-Assisted Separation

Abstract

We investigate the role of a TiN film on epitaxial growth and crystal quality in the void‐assisted separation (VAS) method. Plan‐view TEM images show the TiN film contains numerous nanometer‐scale holes, resulting in a nano‐net structure. X‐ray rocking curve data show the crystal quality of GaN layers on the TiN nano‐net is very high, having the tilt/twist angles of 60/90 arcsec. Numerous small GaN islands were generated on the TiN nano‐net in the beginning of the growth. These islands having crystal facets may introduce the dislocation bending. We show that the TiN film plays a very important role in improving the crystal quality in the VAS method.

Fabrication of Freestanding GaN Wafers by Hydride Vapor-Phase Epitaxy with Void-Assisted Separation

“…Many GaN islands were observed on the surface in the initial stage of the growth. Almost all of these islands originated from the void-containing GaN layer under the TiN nano-net [6]. With continued growth, these islands coalesced, and a flat GaN (0001) surface started to develop.…”

“…5 Â 10 6 cm --2 . The detailed mechanism of the dislocation density reduction is given elsewhere [6].…”

Effect of carbon additive on increases in the growth rate of 2in GaN single crystals in the Na flux method

“…Some approaches such as the hydride vapor phase epitaxy (HVPE) [1][2][3], ammonothermal growth [4][5][6], high-pressure solution growth [7][8][9], and the Na flux [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] methods 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.…”

Sublimation growth of titanium nitride crystals

“…Usui et al [2] studied the role of a TiN layer in GaN epitaxial growth and crystal quality in a void-assisted separation method. The small GaN islands that formed on the TiN nano-net in the beginning of epitaxy have crystal facets that introduce dislocation bending and reduce the threading dislocation density in the GaN layer.…”