Growth Of Crack-Free Gan Epitaxial Thin Films On Composite Si(111)/Polycrystalline Diamond Substrates By Movpe

This paper reports the direct growth by MOVPE of high-quality, crack-free III-nitrides (similar to 350 nm) on composite substrates comprising an ultra-thin Si (111) layer on which polycrystalline diamond (PD) has been deposited. The Si/PD substrates are designed to provide superior heat sinking performance for high power devices. The FWHM of rocking curves of the nitride films is measured to be similar to 1100 arcsec from a GaN/Al0.2Ga0.8N/AlN/Si/PD multilayer structure. As expected from the low coefficient of thermal expansion of diamond, the epitaxial layers are under severe tensile stress. The Si (111) layer is shown to act as a compliant buffer layer between the III-nitride and the PD, i.e. the Si is under a compressive stress under the influence of GaN of larger thermal expansion coefficient, but the structure is mechanically stable. This technique is an obvious economic and technological advantage compared to direct growth of III-nitrides on single crystal diamond. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim