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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 22, Number 2
BKCSDE 22(2)
February 20, 2001 

 
Title
Molecular Orbital Calculations for the Formation of GaN Layers on Ultra-thin AlN/6H-SiC Surface Using Alternating Pulsative Supply of Gaseous Trimethyl Gallium (TMG) and NH3
Author
Seeyearl Seong, Jin-Soo Hwang
Keywords
GaN, CVD, MO-Theory.
Abstract
The steps for the generation of very thin GaN films on ultrathin AlN/6H-SiC surface by alternating a pulsative supply (APS) of trimethyl gallium and NH3 gases have been examined by ASED-MO calculations. We postulate that the gallium culster was formed with the evaporation of CH4 gases via the decomposition of trimethyl gallium (TMG), dimethyl gallium (DMG), and monomethyl galluim (MMG). During the injection of NH3 gas into the reactor, the atomic hydrogens were produced from the thermal decomposition of NH3 molecule. These hydrogen gases activated the Ga-C bond cleavage. An energetically stable GaN nucleation site was formed via nitrogen incorporation into the layer of gallium cluster. The nitrogen atoms produced from the thermal degradation of NH3 were expected to incorporate into the edge of the gallium cluster since the galliums bind weakly to each other (0.19 eV). The structure was stabilized by 2.08 eV, as an adsorbed N atom incorporated into a tetrahedral site of the Ga cluster. This suggests that the adhesion of the initial layer can be reinforced by the incorporation of nitrogen atom through the formation of large grain boundary GaN crystals at the early stage of GaN film growth.
Page
154 - 158
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