Browse Prior Art Database

Method for the Preparation of Lateral Superlattices

IP.com Disclosure Number: IPCOM000118605D
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 6 page(s) / 195K

Publishing Venue

IBM

Related People

Himpsel, FJ: AUTHOR [+2]

Abstract

Disclosed is a general method for fabricating lateral superlattices using stepped crystalline surfaces as templates and substrate-selective chemical vapor deposition for striped film growth. Usable templates include those prepared by cleaving layered crystals at an angle close to the plane of the layers, as well as those formed by decorating a stepped surface of a substrate which need not be layered. In this way, many structures used for microelectronics and data recording and storage can be uniquely and easily fabricated.

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Method for the Preparation of Lateral Superlattices

      Disclosed is a general method for fabricating lateral
superlattices using stepped crystalline surfaces as templates and
substrate-selective chemical vapor deposition for striped film
growth.  Usable templates include those prepared by cleaving layered
crystals at an angle close to the plane of the layers, as well as
those formed by decorating a stepped surface of a substrate which
need not be  layered.  In this way, many structures used for
microelectronics and data  recording and storage can be uniquely and
easily fabricated.

      Since proposed by (1), superlattices have been used quite
successfully in electronic devices such as semiconductor lasers.  The
typical vertical superlattices are comprised of alternating layers of
different materials, but their success has spawned extensions of the
original concept to structures consisting of lateral superlattices,
where alternating stripes of different materials are deposited onto a
surface (2, 3, 4).  For fabrication of quantum devices, the
superlattice periods of interest are smaller than those accessible
with lithographic  methods, and instead, stepped surfaces have been
used in order to achieve  atomic precision.  The latter technique
employs, as a template, the regular step spacing of a surface cut at
an angle of a few degrees from  a low-index crystallographic plane.
However, there are very stringent  requirements on the materials that
can be used and their growth mode.  Lattice match and epitaxial
growth of the overlayer are necessities, and growth must occur by
either a step flow mode or segregation of the growing material to a
step edge.  This effectively reduces the choice of usable substrate
materials to a few III-V compounds.  The invention described here
opens up a much wider class of  materials as possible substrates and
templates for lateral superlattices.

      In this invention, fabrication of the lateral superlattices
begins with preparation of a template exhibiting a striped
structure.  This can be achieved by cutting a single crystal of a
layered compound AB at an angle &theta.  close to the plane of the
layers (Fig. 1), thereby exposing alternating stripes of material A
and B at the surface.  The period of the stripes is controlled by the
angle &theta., which should be between 0 and about 20 degrees.

      There are many possible choices for the substrate, e.g.,
vicinal cuts of the (111) surface of materials with NaCl or CuPt
structure.  The former include many alkali halides, various metal
chalcogenides (e.g., NiO, PbS, PbSe), and transition metal carbides
and nitrides (e.g., NbC, TiC, WN, WC).  Apart from CuPt itself, the
CuPt structure has been found in compound semiconductors under
certain growth conditions, e.g., for GaInP deposited by
organometallic CVD (5, 6, 7).  A third class of useful layered
materials is the Perovskites  with metallic layers.

      Alternativel...