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Trends in Bonding Configuration at SiC/III-V
Semiconductor Interfaces |
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Jin-Cheng Zheng, Hui-Qiong Wang, A. T. S. Wee, and C. H. A. Huan
APPL PHYS LETT 79: (11) 1643-1645 SEP 10 2001 |
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Silicon Carbide (SiC) is a promising substrate material for the
growth of GaN or AlN semiconductors since GaN and AlN are both well
lattice matched to SiC. However, there exist different bonding configurations
at SiC/(III-V) semiconductor interfaces and a systematic study is
needed to explain the difference. |
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Figure 1 shows two bonding models for the (1+1) SiC/(III-V) superlattice:
Si-V and C-III for model A, and Si-III and C-V for model B. The linear-muffin-tin-orbital
(LMTO) band-structure method and local-density functional theory are
used for electronic structure and total energy calculations to elucidate
general trends in bonding configuration for such interfaces. |
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| Figure 1. Two bonding models for the (1+1) SiC/(III-V)
superlattice. |
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The formation energies of different III-V semiconductors are
calculated and the more stable of the two models is the one
with the lower formation energy. This data is used to predict,
as well as verify the bonding configurations. The general trend
is for the formation energy of model A to increase, while that
of model B to decrease as the group V element changes from "N"
to "Sb" as seen in Figure 2a. |
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| There exists a linear relationship between the formation energy
difference and the lattice constant difference and it indicates
that the degree of instability of the bonding configuration
is linearly related to the degree of lattice expansion. The
origin of the bonding configurations is closely correlated to
and can be explained in terms of the charge distribution of
III-V semiconductors. An atom with positive charge indicates
it plays the role of the cation in the compound. In SiC, Si
acts as the cation and C as the anion. From electrostatic arguments,
cations prefer to bond to anions at the interface between two
compounds. The charge distribution in III-V semiconductors is
consistent with the predicted bonding configurations, as shown
in Figure 2b. |
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| Figure 2. Summary of the bonding configuration (a)
of the interface at SiC/(III-V) semiconductors compared
with the bulk charge distribution (b) of element III in
(III-V) semiconductors. For (a), the formation energy
difference in the Y axis is positive when the energy for
B is higher and negative when that for A is higher. |
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