EPITAXIAL SUBSTRATE AND METHOD FOR MANUFACTURING EPITAXIAL SUBSTRATE
First Claim
1. An epitaxial substrate in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of said base substrate, said epitaxial substrate comprising:
- a superlattice layer group in which a plurality of superlattice layers are laminated, said superlattice layer being formed of a first unit layer and a second unit layer made of group-III nitrides having different compositions being alternately and repeatedly laminated; and
a crystal layer made of a group-III nitride and formed above said base substrate, said crystal layer being positioned at an upper side of said superlattice layer group relative to said base substrate,wherein said superlattice layer group has a compressive strain contained therein, and, in said superlattice layer group, the more distant said superlattice layer is from said base substrate, the greater said compressive strain becomes.
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Abstract
Provided is a crack-free epitaxial substrate with reduced warping, in which a silicon substrate is used as a base substrate. The epitaxial substrate includes a (111) single crystal Si substrate, a superlattice layer group in which a plurality of superlattice layers are laminated, and a crystal layer. The superlattice layer is formed of a first unit layer and a second unit layer made of group-III nitrides having different compositions being alternately and repeatedly laminated. The crystal layer is made of a group-III nitride and formed above the base substrate so as to be positioned at an upper side of the superlattice layer group relative to the base substrate. The superlattice layer group has a compressive strain contained therein. In the superlattice layer group, the more distant the superlattice layer is from the base substrate, the greater the compressive strain becomes.
25 Citations
17 Claims
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1. An epitaxial substrate in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of said base substrate, said epitaxial substrate comprising:
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a superlattice layer group in which a plurality of superlattice layers are laminated, said superlattice layer being formed of a first unit layer and a second unit layer made of group-III nitrides having different compositions being alternately and repeatedly laminated; and a crystal layer made of a group-III nitride and formed above said base substrate, said crystal layer being positioned at an upper side of said superlattice layer group relative to said base substrate, wherein said superlattice layer group has a compressive strain contained therein, and, in said superlattice layer group, the more distant said superlattice layer is from said base substrate, the greater said compressive strain becomes. - View Dependent Claims (2, 3, 4, 7, 8, 9)
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5. An epitaxial substrate in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of scud base substrate, said epitaxial substrate comprising:
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a superlattice layer group in which a plurality of superlattice layers are laminated, said superlattice layer being formed of a first unit layer and a second unit layer made of group-III nitrides having different compositions being alternately and repeatedly laminated; and as crystal layer made of a group-III nitride and formed above said superlattice layer group, wherein a second group-III nitride of said second unit layer has an in-plane lattice constant, under a strain-free state, greater than that of a first group-III nitride of said first unit layer, each of said second unit layers is formed so as to be in a coherent state relative to said first unit layer located immediately below, in said superlattice layer group, said superlattice layer formed at an upper position has an increased thickness of said second unit layer. - View Dependent Claims (6, 15, 16, 17)
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10. A method for manufacturing an epitaxial substrate for use in a semiconductor device, said epitaxial substrate having a group of group-III nitride layers formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of said base substrate, said method comprising:
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a superlattice layer group formation step for repeating superlattice layer formation step a plurality of times to thereby form a superlattice layer group in which a plurality of superlattice layers are laminated, said superlattice layer formation step being a step for forming a superlattice layer by alternately and repeatedly laminating a first unit layer and a second unit layer made of group-III nitrides having different compositions; and a crystal layer formation step for forming a crystal layer made of a group-III nitride at a position above said superlattice layer group, wherein in said superlattice layer group formation step, said first unit layer and said second unit layer are formed in such a manner that; a second group-III nitride of said second unit layer has an in-plane lattice constant, under a strain-free state, greater than that of a first group-III nitride of said first unit layer; each of said second unit layers is in a coherent state relative to said first unit layer located immediately below; and said superlattice layer formed at an upper position has an increased thickness of said second unit layer. - View Dependent Claims (11, 12, 13, 14)
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Specification