S. A. Ustin

Structural defects in 3C–SiC grown on Si by supersonic jet epitaxy

3C–SiC thin films have been grown on Si(001) and Si(111) substrates by supersonic jet epitaxy. Cross-sectional high resolution scanning transmission electron microscopy (STEM) is used to study the SiC/Si interface structure and defects in the films. The occurrence of twins is evident in the selected area electron diffraction pattern taken from a SiC/Si(111) heterostructure. A 39° angle between twinned and untwinned {111} planes in the [110] projection is confirmed by x-ray pole figure. Twinning is attributed to the growth on the {111} planes. Pure edge misfit dislocations are found at the interface to accommodate the extreme lattice mismatch in SiC/Si(001) heterostructures. A schematic model of the STEM image reveals that a pair of 60° dislocations intersect to form an edge misfit dislocation. A large number of stacking faults and microtwins are present in SiC thin films grown on both Si(001) and Si(111) substrates. The formation of planar defects is attributed to the coalescence of individual three-dime...

Supersonic jet epitaxy of aluminum nitride on silicon (100)

Single phase aluminum nitride (0001) has been grown on atomically clean silicon (100) substrates (720 °C≥Ts≥620 °C) with dual supersonic molecular beam gas sources. The precursors used were triethylaluminum [TEA; Al(C2H5)3] and ammonia (NH3). The maximum growth rate obtained was 0.1 μm/h. The growth rate was found to depend strongly on the kinetic energy of the incident precursors. Single phase films were grown 200–400 nm thick. Structural x‐ray studies reveal 2θ full widths at half‐maxima between 0.20° and 0.35° for the AlN (0002) peak.

Low-temperature epitaxial growth of cubic SiC thin films on Si(111) using supersonic molecular jet of single source precursors

Abstract Epitaxial cubic SiC thin films have been deposited on Si(111) by supersonic molecular jet epitaxy of the single source precursors of methylsilane (MS), CH 3 SiH 3 , and dimethylethylsilane (DMES), (CH 3 ) 2 SiH(CH 2 CH 3 ), at temperatures in the range 780–950 °C. Single crystalline, crack-free epitaxial cubic SiC thin films were successfully grown on carbonized Si(111) substrates at temperatures as low as 830 °C using MS and DMES. Highly oriented cubic SiC thin films in the (111) direction were obtained on uncarbonized Si(111) substrates at 780 °C using MS and at 950 °C from DMES, However, the growth temperature of DMES was lowered to 830 °C on Si(111) when the substrates were initially carbonized with a supersonic jet of acetylene. Below 780 °C, moreover, only polycrystalline cubic SiC thin films were grown on either carbonized or uncarbonized Si(111) surfaces with MS. The advantage of supersonic molecular jets of the single source precursors employed in this study is evident in that the surface carbonization process may not be necessary, and the deposition procedure is quite simple and safe to handle. Real-time, in situ optical reflectivity was used to monitor the film growth. The as-grown films were characterized in situ by Auger electron spectroscopy (AES) and ex situ by ellipsometry, SEM, FTIR, UV/Visible spectroscopy, and XRD (especially omega and phiscan measurements).

Supersonic jet epitaxy of single crystalline cubic SiC thin films on Si substrates from t-Butyldimethylsilane

Abstract Cubic SiC thin films have been grown by supersonic jet epitaxy (SJE) using the single molecular precursor t-butyldimethylsilane (TBDMS), (CH3)3C–SiH(CH3)2. Single crystal cubic SiC thin films were grown on both carburized and uncarburized Si(100) at a temperature of 830°C. Highly oriented cubic SiC(111) thin films were obtained on carburized and uncarburized Si(111) substrates at 830°C. This growth temperature is much lower than conventional CVD growth temperatures. It is believed that this is the first report of SiC growth using t-butyldimethylsilane.

Supersonic jet epitaxy of silicon carbide on silicon using methylsilane

Abstract Cubic SiC thin films have been epitaxially grown on silicon substrates using the single source precursor methylsilane (H3Si–CH3). Single phase films were grown by supersonic jet epitaxy (SJE) at temperatures as low as 560°C on Si(111) and 600°C on Si(001). Growth rates and crystal quality were found to be strongly dependent on substrate temperature and methylsilane kinetic energy. Films were characterized by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM).

An apparatus for supersonic jet epitaxy of thin films

An ultrahigh vacuum chemical beam epitaxy growth system has been built using multiple supersonic jets as precursors. Supersonic jets provide very high flux to the growth front while maintaining low growth pressures (10−5 Torr). Activation barriers to chemisorption are overcome by using hyperthermal (1–10 eV) precursors for heteroepitaxial growth. Improvement in growth rates and higher degrees of structural orientation are obtained at lower temperatures. Wide band gap semiconductors (SiC, GaN, and AlN) are deposited on silicon substrates using neutral chemical precursors. Epitaxial growth of SiC on silicon has been obtained at the lowest temperatures reported to date using a supersonic jet of methylsilane.

Single crystal wurtzitic aluminum nitride growth on silicon using supersonic gas jets

Highly oriented aluminum nitride (0001) films have been grown on Si(001) and Si(111) substrates at temperatures between 550 C and 775 C with dual supersonic molecular beam sources. Triethylaluminum (TEA;[(C{sub 2}H{sub 5}){sub 3}Al]) and ammonia (NH{sub 3}) were used as precursors. Hydrogen, helium, and nitrogen were used as seeding gases for the precursors. Providing a wide range of possible kinetic energies for the supersonic beams due to the disparate masses of the seed gases. Growth rates of AlN were found to depend strongly on the substrate orientation and the kinetic energy of the incident precursor; a significant increase in growth rate is seen when seeding in hydrogen or helium as opposed to nitrogen. Growth rates were 2--3 times greater on Si(001) than on Si(111). Structural characterization of the films was done by reflection high energy electron diffraction (RHEED) and x-ray diffraction (XRD). X-ray rocking curve (XRC) full-width half-maxima (FWHM) were seen as small as 2.5{degree}. Rutherford back scattering (RBS) was used to determine the thickness of the films and their chemical composition. Films were shown to be nitrogen rich, deviating from perfect stoichiometry by 10--20%. Surface analysis was performed by Auger electron spectroscopy (AES).

Large area supersonic jet epitaxy of AlN, GaN, and SiC on silicon

AlN, GaN, and SiC thin films were grown on 100 mm diameter Si(111) and Si(100) substrates using Supersonic Jet Epitaxy (SJE). Precursor gases were seeded in lighter mass carrier gases and free jets were formed using novel slit-jet apertures. The jet design, combined with substrate rotation, allowed for a uniform flux distribution over a large area of a 100 mm wafer at growth pressures of 1--20 mTorr. Triethylaluminum, triethylgallium, and ammonia were used for nitride growth, while disilane, acetylene, and methylsilane were used for SiC growth. The films were characterized by in situ optical reflectivity, x-ray diffraction (XRD), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE).

Supersonic jet epitaxy: an improved method for nitride deposition

GaN was grown by supersonic jet epitaxy (SSJE), seeding triethylgallium in helium carrier gas. Activated nitrogen was supplied by a microwave plasma source. Single crystalline GaN films were deposited on the Si-face 6H-SiC and the c-plane sapphire substrates at 600--670 C. A cubic SiC buffer layer was grown on Si(111) at 800 C by SSJE using dichlorosilane, acetylene, and a high quality GaN crystal was grown on this template at 630 C. The materials high quality was proved by hard rectifying characteristics of a diode with an N-GaN/{beta}-SiC/P-Si(111) structure.