Yasuichi Masuda

Determination of Donor Densities and Donor Levels in 3C-SiC Grown from Si2(CH3)6 Using Hall-Effect Measurements

Without any assumption of the number of types of impurities, the densities and energy levels of donors in undoped 3C-SiC grown from Si2(CH3)6 are precisely determined by the simple graphical method proposed here, using the temperature dependence of the majority-carrier concentration obtained by Hall-effect measurements. We detect at least three types of donors whose energy levels (ΔED) are 7–14 meV, 46–54 meV and 97–120 meV as measured from the conduction band, although it was reported that ΔED for nitrogen atoms decreased with an increase in the donor density from ~50 meV to ~15 meV. In addition to the ~15 meV donor that was reported in undoped 3C-SiC grown from a mixture of SiH4 and C3H8, at least two donor levels are detected in undoped epilayers grown from Si2(CH3)6. From the viewpoints of donor density and compensation ratio, the quality of undoped 3C-SiC grown from Si2(CH3)6 is better than that of undoped 3C-SiC grown from a mixture of SiH4 and C3H8.

A proposal for CVD growth of 15R-SiC by observing the etch pits on 15R-SiC C-face

Abstract As grown Acheson crystals of 15R-SiC and 6H-SiC were etched by molten KOH. Etch pits peculiar to each polytype were observed both on C-face and Si-face of etched crystals. The inside of etch pit on the C-face was flat. Etch pits on 6H-SiC showed six-fold symmetry, and etching rate toward six equivalent 〈1 1 2 0〉 was the fastest. In case of 15R-SiC, etching rate toward [1 1 0 0] was faster than that of [ 1 1 0 0] , and etch pits showed three-fold symmetry. Etching rate anisotropy between [1 1 0 0] and [ 1 1 0 0] of 15R-SiC was explained by the number of dangling bonds per edge atom. Though the chemical vapor deposition (CVD) growth of 15R-SiC has been conducted on Si-face 8.0° off-oriented toward 〈1 1 2 0〉 , [1 1 2 0] and [ 11 2 0] might not be equivalent in 15R-SiC. If the crystal grew at near-equilibrium condition, the difference between off-orientation toward [1 1 2 0] and [ 11 2 0] might become obvious. Further research is necessary for the CVD growth of 15R-SiC to achieve high quality crystals.

Deep Level Study in Heteroepitaxial 3C-SiC Grown on Si by Hexamethyldisilane

Deep levels in 3C-SiC on Si grown by chemical vapor deposition using hexamethyldisilane (HMDS) were investigated by the deep level transient spectroscopy (DLTS). 3C-SiC epilayers with various thicknesses were grown by changing the growth time. Relatively thin epilayers ( 2.2 µm) showed only one DLTS peak, which corresponds to a defect having an activation energy of about 0.25 eV. This defect is a donor defect and is identical with a defect observed in 3C-SiC grown from SiH4 + C3H8.

Reduction of Hollow Defects in 6H-SiC Single Crystals Grown by Sublimation Boule Growth Technique on (1120) 6H-SiC Substrates

Sublimation boule growth of 6H-SiC on (1120) 6H-SiC substrates was investigated. Hollow defects were generated in the crystals grown on (1120) substrates, and they penetrated along the growth direction to the as-grown surface. A new growth model of SiC on (1120) SiC substrates that distinguishes between two-dimensional growth and three-dimensional growth is proposed. The generation of both the stacking faults and the hollow defects on (1120) substrates was attributable to the three-dimensional growth. The growth conditions were modified and applied to suppress the generation of hollow defects. These conditions included the reduction of the growth temperature in the initial stage of the growth, and the increase of the nitrogen concentration in the vapor phase. Due to the changes in the growth conditions, the density of the hollow defects on (1120) substrates was reduced by one order of magnitude to approximately 103 cm-2. An atomically flat as-grown surface was obtained by the sublimation boule growth technique in nitrogen ambient.

DLTS study of 3C-SiC grown on Si using hexamethyldisilane

n-type 3C-SiC was heteroepitaxially grown on n-type Si(100) substrates using HMDS (hexamethyldisilane) and characterized by DLTS (deep level transient spectroscopy) measurements. In order to investigate relationship of defect density with epilayer thickness, epilayers with various thicknesses were grown. Relatively thin ( 2.2μm thick) epilayers contain a defect with an activation energy of 0.25eV. This defect level is slightly shallower than that in 3C-SiC grown by SiH 4 and C 3 H 8 (∼0.3eV).