Effect of the Growth Rate on the Structure and Stacking Disorder of SiC Crystals Grown in the Cavity of Lely's Procedure

Abstract

The relation between structure of SiC and growth rate was studied at 2500°C experimentally. In this experiment, the setting of the growth condition was improved by limitting the zone of recrystallization in the growth cavity and supersaturation in the cavity was changed in several steps by the use of cavity wall and thermo-insulator.
Summerized results are as follows;
(1) In the region of low supersaturation (growth rate for the direction of a-axis less than 90 Å/sec), crystals having c-axis elongated columnar habit were obtained. These crystals were mainly pure 6 H type and have little stacking disorder along c-axis.
In these region, there also obtained plate like crystals. These crystals often showed the coalescence of polytypes, but have little stacking disorder. This difference for the coalescence of several polytypes and crystal habit seemed to depend on the orientation of crystals in the growth cavity.
(2) In the region of high supersaturation (growth rate for the direction of a-axis greater than 90 Å/sec), well developed hexagonal plate like crystals were obtained. These crystals frequently showed the coalescence of polytypes and stacking disorder along c-axis.
(3) Obtained crystals in this experiment were mainly 6 H and 15 R type and almost all crystals include 6 H structure.
4 H and 21 R showed smaller relative amount than 6 H and 15 R. Long c-period structure were also found, but all of these showed stacking disorder along c-axis and coalescence with 6 H.
(4) Accurate memory of stacking for the columnar crystals seemed to depend on screw dislocations which have the end on the (0001) surface that showing higher growth rate. In this experiment, some of these crystals showed a few growth spirals on their (0001) surface located on the top of these crystals.
On the contrary, (0001) surface of plate like crystals grown in the high supersatulation region, together growth spirals, the existence of two-dimensional growth layers were frequently observed.
(5) Corresponding to the phenomenons shown (1), (2) and (4), the value, about 1.2-1.4% was calculated for the critical supersaturation at 2500°C.