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Growth of III-V and Other Nitrides by Gas Source Molecular Beam Epitaxy

IP.com Disclosure Number: IPCOM000114305D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 4 page(s) / 146K

Publishing Venue

IBM

Related People

Strite, S: AUTHOR

Abstract

The III-V nitride semiconductors are highly suitable for many device applications as a result of their large bandgaps and outstanding thermal stability. Device development is presently limited by the ability of crystal growers to introduce a stoichiometric amount of nitrogen into the crystal lattice. Present day techniques rely on high substrate temperatures or a remote plasma to crack the N containing source gas. Each approach introduces significant difficulties. In this Bulletin, a Gas Source Molecular Beam Epitaxy (MBE) growth technique in which NH3 is cracked remote from the substrate is proposed for the growth of the III-V nitride semiconductors and other N compounds. It is argued that this approach can overcome the major difficulties faced by present day growth techniques.

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Growth of III-V and Other Nitrides by Gas Source Molecular Beam Epitaxy

      The III-V nitride semiconductors are highly suitable for many
device applications as a result of their large bandgaps and
outstanding thermal stability.  Device development is presently
limited by the ability of crystal growers to introduce a
stoichiometric amount of nitrogen into the crystal lattice.  Present
day techniques rely on high substrate temperatures or a remote plasma
to crack the N containing source gas.  Each approach introduces
significant difficulties.  In this Bulletin, a Gas Source Molecular
Beam Epitaxy (MBE) growth technique in which NH3 is cracked remote
from the substrate is proposed for the growth of the III-V nitride
semiconductors and other N compounds.  It is argued that this
approach can overcome the major difficulties faced by present day
growth techniques.

      GaN, AlN and InN are extremely promising semiconductors for
optical and electronic device applications (1).  Present day device
development is limited by the quality of the material which is grown
by either metalorganic vapor phase epitaxy (MOVPE) or plasma enhanced
MBE.  The challenge of nitride growth is to incorporate a
stoichiometric amount of nitrogen into the lattice.  This is
difficult due to the relative inertness of most nitrogen containing
molecules which is directly attributable to the strength of N bonds.
MOVPE and MBE each have advantages and disadvantages for
incorporating nitrogen and producing good nitride material.  Here, it
is proposed to extend gas source MBE to the III-V nitride
semiconductors and potentially any other nitrogen containing compound
because of this approach's potential for combining the advantages of
MOVPE and MBE, while avoiding the inherent disadvantages of each.

      Overview of present day growth techniques - The highest quality
GaN material grown today is deposited by MOVPE on sapphire substrates
at a substrate temperature in the neighborhood of 1000 degrees C (2).
The high substrate temperature is required to thermally crack the NH3
source gas at the substrate, but introduces numerous undesirable
effects.  Because GaN substrates don't exist, all III-V nitride
semiconductors must be grown heteroepitaxially.  The most popular
substrates, sapphire and SiC, are not thermally matched with GaN and
AlN (Fig. 1) so post-growth cooling introduces a large defect density
and residual strain as a result of the different thermal expansion
coefficients.  Also, it is difficult to incorporate InN (3) due to
large amounts of In desorption at such high growth temperatures.  The
strong dependence of desorption on temperature makes it very
difficult to control the exact InN mole fraction, and therefore the
exact wavelength of emission when an InGaN active layer is used in a
device structure.  The high temperature is also expected to increase
dopant diffusion and segregation.  It is desirable, for these
reasons, to develop a lower...