In an attempt to achieve an InP–Si
heterointerface, a new and generic method, the corrugated epitaxial lateral
overgrowth (CELOG) technique in a hydride vapor phase epitaxy reactor, was
studied. An InP seed layer on Si (0 0 1) was patterned into closely spaced
etched mesa stripes, revealing the Si surface in between them. The surface with
the mesa stripes resembles a corrugated surface. The top and sidewalls of the
mesa stripes were then covered by a SiO2 mask after which the line openings on
top of the mesa stripes were patterned. Growth of InP was performed on this
corrugated surface. It is shown that growth of InP emerges selectively from the
openings and not on the exposed silicon surface, but gradually spreads
laterally to create a direct interface with the silicon, hence the name CELOG.
We study the growth behavior using growth parameters. The lateral growth is
bounded by high index boundary planes of {3 3 1} and {2 1 1}. The atomic
arrangement of these planes, crystallographic orientation dependent dopant
incorporation and gas phase supersaturation are shown to affect the extent of
lateral growth. A lateral to vertical growth rate ratio as large as 3.6 is
achieved. X-ray diffraction studies confirm substantial crystalline quality
improvement of the CELOG InP compared to the InP seed layer. Transmission
electron microscopy studies reveal the formation of a direct InP–Si
heterointerface by CELOG without threading dislocations. While CELOG is shown
to avoid dislocations that could arise due to the large lattice mismatch (8%)
between InP and Si, staking faults could be seen in the layer. These are
probably created by the surface roughness of the Si surface or SiO2 mask which
in turn would have been a consequence of the initial process treatments. The
direct InP–Si heterointerface can find applications in high efficiency and
cost-effective Si based III–V semiconductor multijunction solar cells and
optoelectronics integration.
Source:IOPscience
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