This paper reports the direct growth by MOVPE of high-quality, crack-free III-nitrides (∼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 ∼1100 arcsec from a GaN/Al 0.2Ga 0.8N/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.
|Number of pages
|Physica Status Solidi (C) Current Topics in Solid State Physics
|Published - Mar 2012