Single Crystal Gallium Nitride on Silicon Using SiC as an Intermediate Layer
- PDF / 1,600,911 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 108 Downloads / 157 Views
ABSTRACT GaN films have been grown atop SiC intermediate layers on Si(001) and Si(111) substrates 0 using supersonic jet epitaxy (SJE). GaN growth temperatures ranged between 600 C and 775 °C. Methylsilane (H 3 SiCH 3 ) was used as the single source precursor for SiC growth and triethylgallium (TEG) and ammonia (NH 3) were the sources for GaN epitaxy. The GaN growth rate was found to depend strongly on substrate orientation, growth temperature, and flux. Structural characterization of the films was done by transmission electron diffraction (TED) and x-ray diffraction (XRD). Growth of GaN on SiC(002) produces a cubic or mixed phase of cubic and wurtzite depending on growth conditions. Growth on SiC(111) produces predominantly wurtzite GaN(0002). Minimum rocking curve widths for GaN(0002) on SiC/Si(111) and GaN(002) on SiC/Si(001) are 0.60 and 1.50, respectively. Cross Sectional Transmission Electron Microscopy (XTEM) was also performed.
INTRODUCTION GaN and its alloys are receiving much attention with regard to development of blue and UV laser diodes. For the most part research has been focused on the wurtzite GaN phase on sapphire. However, difficulties arise in cleavage and formation of back contacts in this system. Zinc-blende growth on a conductive substrate has the potential to solve these problems. Cubic crystals have a higher crystallographic symmetry than their hexagonal counterparts. Thus /-GaN is expected to have lower phonon scattering, better doping characteristics, and higher mobility. Large-area conductive low-cost Si and GaAs substrates are available for /3-GaN epitaxy. Incorporation of GaN devices onto already processed Si wafers holds great promise for inter-chip communication in Si VLSI circuits. Since the lattice constant of Si (5.43 A) is much larger than that of GaN (4.52 A) we shift our attention to growth on /3-SiC (4.36 A). We discuss growth of GaN films on SiC/Si(001) and SiC/Si(1ll) substrates.
EXPERIMENTAL PROCEDURE SiC and GaN films were grown by supersonic jet epitaxy (SJE), a chemical beam epitaxy technique that utilizes supersonically expanded molecular jets as sources. Effusion sources are constrained to energies below 1 eV, whereas energies up to 10 eV can be achieved using supersonic sources. This is done through the use of mixed gas seeding techniques[1], i.e. by mixing a heavy gas source (TEG, NH 3 , or H3 SiCH 3 ) in a low concentration with a lighter gas source (H 2 , He, or N2 ). Growth is performed on both Si(001) and Si(l1l) substrates. RHEED patterns taken at room temperature of cleaned Si(111) and Si(001) substrates show clear evidence of 7x7 and 2xl reconstruction, respectively, confirming the extent of the cleanliness. X-ray analysis was done on a Scintag PAD-X diffractometer (Cu K0 , A=1.5401 A). Some rocking curves and azimuthal scans were performed on a four circle diffractometer at the Cornell High Energy Synchrotron Source (A=1.215 A). Cross-sectional TEM analysis was conducted in a Vacuum Generators HB501UX scanning transmission electron microscope operated at 100
Data Loading...
