Dopant incorporation efficiencies of SiC crystals grown on { 1100}-face
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Mat. Res. Soc. Symp. Proc. Vol. 423 c 1996 Materials Research Society
work, so that the incorporation efficiencies are discussed by comparing the dopant concentrations in the crystals grown with different front facets. EXPERIMENTAL PROCEDURE Crystal Growth SiC crystals were grown in a graphite crucible with a lid. SiC source powder was laid at the bottom of the crucible and the seed crystal attached on the lid. SiC crystals grow by vapor transport from a source powder (2295 C') to a seed (2230 V0) under Ar ambient pressure of 1 Torr. Abrasivegrade SiC powder (Showa Denko) was used as a source powder. The 6H-SiC seeds with a I 1100) face were fabricated by cutting from an ingot grown on (0001) faced seed by a sublimation method, since Acheson crystals are not thick enough in the c-direction. The crystals were grown on the ( 1100) oriented seed with 10 mm in diameter. The growth run for 24 hrs. The impurities were supposed to derive from the source material and the graphite crucible. Intentional doping was not carried out in this experiment. Characterization of Crystals
wafer-I wafer-II
The grown ingot was sliced parallel to the (1100) face at a distance of 2 min from the top of the crystal (ref. fig. 1). The sliced wafer was polished to a thickness of 1 mm (wafer-A). The concentrations of impurities were determined in the central area (
8mm) of the wafer-A by
Glow Discharge Mass Spectroscopy (GDMS). The results were compared with those of wafers grown on (0001) Si-face and (0001) C-face. Additionally, three c-cut wafers were sliced out of the grown ingot to investigate the distributions of impurities in the crystal. They were sampled from the parts where the SiC grew with a (1100) facet (wafer-I), with a {1 On) facet which is inclined from ( 1100) face to Si-face (wafer-II) and with a 1 ln0n) facet which inclined to C-face (wafer-Ill). (n : natural numbers) Absorption coefficients were measured in the visible light range for the qualitative estimation of nitrogen concentration on these wafers.
584
wafer-IlI
(1 f00)..: wafer-.A_.-, ....... 44 Si-face (0001) (0001)(0001) Seed
-4---
C-face
2 :
Fig. 1 Schematic view of grown ingot and sampled wafers.
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............ ,_ . rig. 4..uutvlew or me ai.. ingot grown on (11001 faced seed. The maximum diameter was about 17 mm.
RESULTS AND DISCUSSIONS
Grown Cystal Figure 2 shows the SiC ingot grown on the (11001 faced seed. The ingot had growing facets of three (11001 faces and their linking fI1On) faces and 11On) faces. The growth rate was approximately 8mm / 24hrs in height. Figure 3 shows the wafer-A horizontally sliced with the (1100) face from the ingot. This figure indicates that the wafer-A consists of three regions with different color contrast, which are central area, Si-face side area and C-face side area of the wafer. Si-face side area was greener. On the other hand, C-face side area was colorless and striped due to high stacking fault densities. This suggests that the dopant incorporation efficiencies are different on these three areas. The c-cut waf
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