Abstract
The effects of a deviation in the fraction of the components in the ambient phase of a stoichiometric AB compound, such as GaN or SiC crystals, on the surface roughness and step self-assembly and disassembly on a vicinal surface are studied using the Monte Carlo method based on a staggered restricted solid-on-solid (st-RSOS) model at equilibrium. The (001) and (111) surfaces are typical examples of non-polar and polar surfaces, respectively. Although a stoichiometric deviation of the ambient phase does not affect the surface energy of a non-polar surface, it affects that of polar surfaces such as the 
 
 
 
 
 (
 111
 )
 
 A
 
 
 
 and 
 
 
 
 
 (
 111
 )
 
 B
 
 
 
 surfaces. We found that the vicinal surface of an AB compound is atomically smooth and globally rough. Globally, the vicinal surface is not affected by a stoichiometric deviation in the ambient phase. In contrast, in a small area, the structure of the vicinal surface is affected by a stoichiometric deviation in the ambient phase. The vicinal surface consists of local double and quadruple steps. The characteristic length 
 
 
 
 L
 
 M
 F
 L
 
 
 
 
 , which separates the global length scale region and the local length scale region, has a maximum value of 
 
 
 
 156
 a
 
 
 
 in the present study, where a is the lattice constant. When temperature decreases, 
 
 
 
 L
 
 M
 F
 L
 
 
 
 
 can become large.
Highlights
Stoichiometric two-component semiconductors such as SiC, GaN, and GaAs have potential applications in power devices
Figure 7. (001) facet shapes on the equilibrium crystal shape (ECS) and polar graphs of step tension γ(φ) calculated using the imaginary-path-weight random walk (IPW) method [75,76] based on the 2D lattice gas model. ∆μ A /e = (a) 0.0, (b) 1.0, (c) 2.0, and (d) 3.0
To obtain discontinuous surface tension at low temperature, the point-contact-type step–step attraction that originates from the quantum mechanical interactions between steps [10] is required
Summary
Stoichiometric two-component semiconductors such as SiC, GaN, and GaAs (called AB compounds) have potential applications in power devices. For an AB compound, the polar A surface has lower energy than that of the B surface if the ambient phase is A-rich [38,39,40] In this circumstance, macrostep formation may occur due to component deviation in the ambient phase. To clearly observe the effects of the change due to component deviation in the ambient phase at equilibrium, we do not consider the second-nearest-neighbor interaction between atoms [51] in crystals, the Ehrlich–Schwoebel effect [52,53], elastic interactions [54], surface reconstruction [14], and point-contact-type step–step attraction [2]. The border between local behavior and global behavior with respect to vicinal surface roughness is discussed
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