SIC SINGLE CRYSTAL(S) DOPED FROM GAS PHASE
An apparatus for sublimation growth of a doped SiC single crystal includes a growth crucible, an envelope, a heater, and a passage for introducing into the envelope from a source outside the envelope a doping gas mixture. The gas mixture includes a gaseous dopant precursor that, in response to entering a space between the growth crucible and the envelope, undergoes chemical transformation and releases into the space between the growth crucible and the envelope dopant-bearing gaseous products of transformation which penetrate the wall of the crucible, move into the crucible, and absorb on a growth interface of a growing SiC crystal thereby causing doping of the growing crystal. A sublimation growth method is also described.
1 . A method of growing a doped silicon carbide (SiC) single crystal by sublimation, comprising:
providing SiC source material and a SiC single crystal seed in spaced relation within a growth crucible;
holding the growth crucible in an envelope, and providing passages for a gas between an exterior surface of the growth crucible and an interior surface of the envelope;
heating the SiC source material to form sublimated material, establishing a temperature gradient between the SiC source material and the SiC single crystal seed, and causing the sublimated material to be transported to and precipitate on the SiC single crystal seed; and
using the passages to introduce into the envelope, from a source outside the envelope, a doping gas mixture including a gaseous dopant precursor, and heating the gaseous dopant precursor, within the passages, to a temperature between 2000° C. and 2400° C., such that the gaseous dopant precursor undergoes a chemical transformation and releases into the space between the growth crucible and the envelope dopant-bearing gaseous products which penetrate the crucible wall, move into the crucible, and absorb on a growth interface of a growing SiC crystal.
2 . The method of claim 1 , further comprising holding the envelope in a furnace chamber while the growth crucible is disposed in the envelope.
3 . The method of claim 1 , wherein the doped SiC single crystal is of 4H or 6H polytype.
4 . The method of claim 1 , wherein the doping gas mixture includes a carrier gas.
5 . The method of claim 4 , wherein the carrier gas is an inert gas.
6 . The method of claim 5 , wherein the inert gas includes gaseous additives of hydrogen and/or halogen.
7 . The method of claim 4 , wherein the gaseous dopant precursor is chosen from the group of volatile hydride compounds, volatile halogenated compounds, and volatile metallo-organic compounds.
8 . The method of claim 7 , wherein the gaseous dopant precursor is phosphine (PH 3 ).
9 . The method of claim 7 , wherein the gaseous dopant precursor is trimethyl aluminum (Al(CH 3 ) 3 ).
10 . The method of claim 7 , wherein the gaseous dopant precursor is vanadium tetrachloride (VCl 4 ).
11 . The method of claim 1 , wherein the growth crucible has no open passages for gas entry or escape.
12 . The method of claim 1 , wherein the growth crucible and the envelope are formed from graphite.
13 . The method of claim 11 , wherein the envelope is formed from graphite treated to have reduced permeability.
14 . An apparatus for sublimation growth of a doped SiC single crystal, comprising:
a growth crucible, having a wall and an exterior surface, for holding a silicon carbide (SiC) source material and a SiC single crystal seed in spaced relation;
an envelope, having an interior surface, for holding the growth crucible in the envelope in spaced relation such that space for a gas exists between the exterior surface of the crucible and the interior surface of the envelope;
a heater for heating the growth crucible to sublime the SiC source material, and for forming a temperature gradient between the SiC source material and the SiC single crystal seed that causes the sublimated SiC source material to be transported to and precipitate on the SiC single crystal seed and thereby grow a SiC crystal on the SiC single crystal seed; and
a passage for introducing into the envelope from a source outside the envelope a doping gas mixture that includes a gaseous dopant precursor that, in response to entering the space between the growth crucible and envelope, undergoes chemical transformation and releases into the space between the growth crucible and envelope dopant-bearing gaseous products of transformation which penetrate the wall of the crucible, move into the crucible and absorb on a growth interface of a growing SiC crystal thereby causing doping of the growing SiC crystal.
15 . The apparatus of claim 14 , further comprising a furnace chamber for holding the envelope while the growth crucible is disposed in the envelope.
16 . The apparatus of claim 14 , wherein the gas mixture includes a carrier gas.
17 . The apparatus of claim 16 , wherein the carrier gas is an inert gas.
18 . The apparatus of claim 17 , wherein the inert gas includes gaseous additives of hydrogen and/or halogen.
19 . The apparatus of claim 16 , wherein the gaseous dopant precursor is chosen from the group of volatile hydride compounds, volatile halogenated compounds, and volatile metallo-organic compounds.
20 . The apparatus of claim 19 , wherein the gaseous dopant precursor is phosphine (PH 3 ).
21 . The apparatus of claim 19 , wherein the gaseous dopant precursor is trimethyl aluminum (Al(CH 3 ) 3 ).
22 . The apparatus of claim 19 , wherein the gaseous dopant precursor is vanadium tetrachloride (VCl 4 ).
23 . The apparatus of claim 14 , wherein the growth crucible and the envelope are formed from graphite.
24 . The apparatus of claim 23 , wherein the envelope is formed from graphite treated to have reduced permeability.