Compliant Silicon-on-Insulator Substrate for GaN Epitaxy

The use of silicon as the supporting template for nitride growth offers obvious advantages in terms of low cost and the prospects for integration of photonic devices with the mature silicon technology. However, GaN has a large lattice mismatch with respect to Si while SiC is closely lattice matched to GaN. Thus we propose an approach for growing very high quality single crystal films of SiC on Si which will solve the nitride substrate problem by providing an excellent silicon-based substrate for GaN deposition. Our approach will keep the lattice points for the SiC layer coherent with the silicon substrate (no kinks); thus all of the dislocations will remain in the plane of the junction, passing out of the material at the edges of the wafer. We rely on a non-thermodynamic equilibrium growth technique, supersonic jet epitaxy, that can supply kinetic energy for growth at low temperatures where lattice relaxation cannot readily occur, and a compliant substrate which will relieve the stress by generating dislocation in a thin layer of Si on Sio 2 before the SiC film can relax. Phase I will concentrate on substrate preparation and parameters for depositing highly perfect SiC films at low temperatures. An optional task will explore the effect of alternate substrate orientations. Phase II will concentrate on optimizing the compliant substrates and developing high performance nitride devices on them.