Low temperature chemical vapor deposition growth ofb-SiCon (100) Si using methylsilane and device characteristicsC. W. Liua)Department of Electrical Engineering, National Taiwan University, Taipei 106, TaiwanJ. C. SturmDepartment of Electrical Engineering, Princeton University, Princeton, New Jersey 08544~Received 7 February 1997; accepted for publication 29 July 1997!The growth properties ofb-SiC on ~100! Si grown by rapid thermal chemical vapor deposition,using a single precursor ~methylsilane! without an initial surface carbonization step, wereinvestigated. An optimun growth temperature at 800 °C was found to grow single crystallinematerials. A simple Al Schottky barrier fabricated on n-type SiC grown on Si substrates exhibiteda ‘‘hard’’ reverse breakdown of 13 V with a positive temperature coefficient of 23 102 4°C2 1upto 120 °C, indicating an avalanche mechanism. A Pt Schottky barrier fabricated on n-type SiCgrown on tilted Si substrates to improve the surface morphology exhibited a breakdown voltage of59 V, with a negative temperature coefficient. From the analysis of the electrical field distribution,the breakdown probably occurred at interface defects between SiC and Si, as suggested by Ramanspectroscopy. To investigate minority transport behavior, SiC/Si heterojunction bipolar transistors~HBTs! were fabricated and compared to Si bipolar junction transistors. The collector currents of theSiC/Si HBTs were similar to those of Si control transistors, because both devices had the same basestructures. Compared to Si control transistors, the base currents of SiC/Si HBTs increased. It seemsthat the interface defects between Si and SiC act as recombination centers to deplete back-injectedholes, instead of being the barrier to stop hole currents, and thus to increase the base currents ofSiC/Si HBTs. © 1997 American Institute of Physics. @S0021-8979~97!03921-2#I. INTRODUCTIONThe unique thermal and electronic properties of SiCmake it a promising material for electronic and optoelec-tronic devices designed to operate in extreme conditionssuch as high voltage, high temperature, high frequency, andhigh radiation. SiC has many different one-dimensionalpolytypes ~different stacking sequences!. A repetitive ABCstacking sequence yields a zincblende structure, referred toas 3C orb-SiC. The other about 170 non-cubic crystals arereferred to as thea-SiC family. Recently, most of the re-search activities and progress have been made ona-SiC,primarily 6H and 4H,1,2because of the mature bulk crystaltechnologies.3There are no suitable substrates ofb-SiC crys-tals, butb-SiC epilayer has been grown in the past on Si~100! substrates, despite a 20% mismatch of lattice constantsand an 8% mismatch of thermal expansion coefficients be-tweenb-SiC and Si. Conventionally, the chemical vapordeposition growth ofb-SiC on Si requires high growth tem-peratures (>1300 °C!4using separate precursors such asSiH4for Si and C3H8for C, and an initial high temperaturesurface carbonization step,5,6which prevents the possibilityof integration with silicon-based devices. Furthermore, thelow material quality is reflected in very leaky Schottky bar-riers with the highest reported soft breakdown of only 8–10V.7In this study, we report growth properties of cubic SiCon ~100! Si grown at temperature as low as 700 °C using asingle gas precursor ‘‘methylsilane’’ without the carboniza-tion step, first demonstrated by Golecki et al.8We describethe material properties of the films using x-ray diffraction,Raman scattering, Fourier transform infrared absorption, andtransmission electron microscope, and then discuss Schottkybarriers and Si/SiC heterojunction bipolar transistors fabri-cated on these films.II. GROWTHDue to the lack of suitableb-SiC substrates,b-SiC wasgrown on Si ~100! substrates. The SiC films were depositedon tilted ~4° towards^110&) and nontilted Si substrates~within 1° off! with a diameter of 100 mm by rapid thermalchemical vapor deposition ~RTCVD! at a growth tempera-ture of 700–1100 °C. The growth pressure was 1 Torr with a1.5 sccm methylsilane ~SiCH6) flow and a 500 sccm hydro-gen flow. The growth temperature ~700–800 °C! was accu-rately determined by the infrared transmission technique.9Growth temperatures higher than 800 °C were controlled bythe tungsten-halogen lamp power which was previously cali-brated with a thermocouple welded onto a Si wafer. The SiCthickness was measured by fitting the optical reflection spec-tra from 500 to 700 nm with the SiC index of refraction of2.6. Since the temperature is not uniform across the wafer~the edge is about 50 °C lower than the center!, the thicknesswas measured at the spot very close to the position where thetemperature was monitored ~near the center of the wafer!.Figure 1 gives the Arrhenius plot of the growth rate of SiCon nontilted ~100! Si. The growth rate in the range 700–800 °C varied exponentially with the inverse of temperatureand the activation energy for this surface-reaction-limitedgrowth was 3.6 eV. This is higher than that of pure silicongrowth using silane as a precursor (;1.7 eV!10and mayreflect the strong C–H bonding energy. At a higher growtha!Electronic mail: [email protected] J. Appl. Phys. 82 (9), 1 November 1997 0021-8979/97/82(9)/4558/8/$10.00 © 1997 American Institute of PhysicsDownloaded 14 Nov 2001 to 128.112.49.42. Redistribution subject to AIP license or copyright, see http://ojps.aip.org/japo/japcr.jsptemperature ~800–1100 °C!, the growth rate had a weak tem-perature dependence, indicating mass-transport-limitedgrowth.The crystallinity of the films was studied by x-ray dif-fraction ~XRD! and transmission electron microscope~TEM!. For the films grown at 750 °C, the XRD spectrum@Fig. 2~a!# of an 80 nm film on nontilted substrates exhibiteda single crystalline feature with a broad unresolved Cu Ka1and Cu Ka2~400! peak @full width half maximum ~FWHM!of 2uis about 1.6°]. But the TEM diffraction pattern @Fig.2~b!# of the same sample showed evidence of some slightlyin-plane rotated textures and very fine spots in the^110&direction. This indicates the poor crystallinity of the 750 °Cfilms. The crystallinity can be improved by increasing thegrowth temperature to 800 °C. The XRD spectrum @Fig.3~a!# of a 0.23mm SiC film grown at 800 °C on nontiltedsubstrates showed that the FWHM of unresolved Cu Ka~400! peak was as small as 0.75°, which was similar to thevalue ~0.65–0.7°! of 0.3mm commercial