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Presented at the Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Symposium held in San Jose, California on 5-7 March 2007. Document contains briefing charts only. The original document contains color images.

An atomic layer epitaxy deposition system configured for the growth of thin films of the III-V nitrides of A1, Ga and In has been designed, constructed and commissioned. The system allows the introduction of up to 16 gases without mixing. Self-terminating growth of crystalline GaN films has been achieved on single crystal wafers of (0001) alpha(6H)-SiC. Results of analyses via Auger spectroscopy, electron microscopy and electron diffraction are described. Deposition of AIN and GaN via gas-source MBE was also continued during this period. The principal emphasis concerned the initial stages of growth of both compounds on the substrates of (00001) alpha(6H)-SiC and (0001) sapphire, as determined using X-ray photoelectron spectroscopy. An initial layer of silicon nitride formed on the surface of SiC prior to the deposition of either nitride. The deposition of GaN on sapphire followed the Stranski- Krastanov mode of nucleation and growth, while on SiC, characteristics of three- dimensional growth were evident. By contrast, AlN grew initially in a layer-by- layer mode. Deposition of GaN on vicinal (100) Beta-SiC during UV irradiation resulted in the formation of a new 4H polytype of this material. Deposition of BN via gas-source MBE on Cu(110) resulted in nanocrystalline cBN; films grown on (111) Cu resulted in h-BN (graphitic phase). Similar studies using Si(100) substrates also resulted in the occurrence of cBN. The occurrence of the cubic polytype was enhanced while that of h-BN was discouraged with the use of the UV light at 400-500 deg C.

The primary focus of the research for this grant has been the atomic layer epitaxy (ALE) of Si; however, the ALE of SiC has also received serious consideration. A Computer assisted study, based on the free energy minimization of a thermodynamic system undergoing equilibrium reactions has shown that the progressive decomposition of SiH2Cl2 (the Si precursor of choice in this study) results in the products of SiCl2, H2, SiH2Cl2, HCl and Si. Moreover, above 600 C, SiCl2 is stable. Thus SiCl2 adsorbed onto the surface will not decompose. It is predicted to react with H2, forming Si on the surface.