This Small Business Innovation Research (SBIR) Phase I project explores the use of low-defect, high-quality silicon carbide on ultrathin silicon-on-insulator (SOI) structures as a lattice-matched substrate for growth of GaN by atomic layer epitaxy (ALE). Recent experiments have fabricated ultrathin Si on SiO2 as thin as 140 Angstroms by the low-energy Separation by IMplantation of OXygen (SIMOX) process. SiC thin films will be fabricated by carbonizing the ultrathin Si top layer of SIMOX wafers. The carbonization technique has produced the lowest defect density in epitaxial SiC on Si; however, due to different lattice constants, a strained layer exists at the interface which limits the usefulness of this material for device applications. Thin Si films allow rapid conversion of the entire Si layer to SiC and result in SiC in contact only with SiO2, which is amorphous and softens at the carbonization temperature. In the absence of a lattice mismatch, the source of stress is eliminated (similar to SIMOX), thus paving the way for formation of a high-quality SiC layer. Preliminary work on the growth of SiC on ultrathin SIMOX structures suggests very good quality SiC as compared to those grown on thick SIMOX or bulk Si. Phase I will produce SiC films under varying material and processing conditions, and GaN will be grown by ALE on the lowest-defect material. If approved, Phase II would include optimization of processing parameters, and fabrication of device structures. Fabrication of large-area, inexpensive, Si-based substrates for growth of low-defect SiC and GaN films are the basis for radiation-hard, high-temperature electronics. These substrates are essential for integration of LEDs, lasers, detectors, and a variety of other devices into silicon-microelectronic chips.
