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Also known as “carborundum”
Occurs naturally (although very rare) as moissanite
While rare naturally on Earth, common form of stardust
First synthetically created in 1893
Initially used as an abrasive
Background
moissanite
Used as a detector in early radios
1907 - First LED Semiconductor Can be doped n-type with
N, P p-type with Al, B, Ga, Be B substitutes C, while Al
substitutes Si (produce different type semiconductors)
Role in Electronics
SiC monocrystal
250 crystalline forms! Three most common polytypes: (α) 6H-SiC
(hexagonal), (β) 3C-SiC (lone cubic), and 4H-SiC (hexagonal)
α-SiC is the most common Pure SiC is colorless – black color comes
from Fe impurities, rainbow shine is from a passivation layer of SiO2
Structure and Properties
Comparison of n-type CVD film grown on the C-face of 6H-SiC to p-type CVD film grown on Si-face of 6H-SiC
Both samples show ZPL’s P0, R0, S0 characteristic of N-doped 6H-SiC
Come from recombination radiation of exciton (hole-electron pair) in a four-particle neutral donor complex at three inequivalent donor sites
Luminescence measurements of 6H-SiC
In C-face film, prominent features below ZPL are phonon replicas of P center
Indicates strong N-doping In Si-face spectrum, three features denoted
4A, I, A0
4A – acceptor four-particle neutral complex A0 associated with Ti in 6H-SiC
Luminescence measurements of 6H-SiC
In C-face, lines due to two phonon replicas of the P line
Combinations of the P line phonon replicas and a center of the zone TO phonon are seen
In Si-face, ZPL of Ti center, A0, B0, C0, and phonon replicas are marked
Luminescence measurements of 6H-SiC (higher wavelength)
Comparative optical investigations of sintered and monocrystallineblack and green silicon carbide (SiC)
H. Werheit and K.A. Schwetz
Solid-state sintering: making a substance from powder by heating it to just below its melting point
Liquid-phase sintering: uses an additive that will melt before matrix phase
Capillary action pulls liquid into pores, grains rearrange into a better packing arrangement
Atoms preferentially go into solution and precipitate in areas of lower chemical potential – called “contact flattening”
Sintered SiC
S-SiC (solid-state sintered) and LPS-SiC (liquid-phase sintered) ordinarily only seen in black only
New LPS process can create green LPS-SiC Uses α-SiC powder S-SiC: doped with 0.2% B LPS-SiC: doped with 1.2% Al, 0.3% N, 0.1%
O Mixed SiC(Al,N,O) crystal shell, pure SiC
core Green is obtained from removal of free
carbon
Sintered SiC
G. Pensl and W.J. Choyke, “Optical and Electrical Characteristics of SiC”. Physica B, 185, 264-283 (1993).
H. Werheit and K. A. Schwetz, “Comparative optical investigations of sintered and monocrystalline black and green silicon carbide (SiC)”. Journal of Solid State Chemistry, 177, 580-585 (2004).
References