Epitaxial substrate and process for producing epitaxial substrate
A technology for epitaxial substrates and manufacturing methods, applied in chemical instruments and methods, semiconductor/solid-state device manufacturing, crystal growth, etc., can solve problems such as low electron mobility, reduced leakage current or withstand voltage, cracks, etc., to suppress accumulation. , Excellent voltage resistance, small bending effect
Inactive Publication Date: 2013-01-09
NGK INSULATORS LTD
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Problems solved by technology
However, the crystalline quality of the resulting GaN film is by no means better than when SiC or sapphire is used as the base substrate
Therefore, in the case of producing electronic devices such as HEMTs using existing technologies, there are problems such as low electron mobility, leakage current when turned off, or lower withstand voltage.
[0013] In addition, in the method disclosed in Patent Document 4, since large convex bends are intentionally generated during device fabrication, cracks may occur during device fabrication depending on layer formation conditions.
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[0100] As an example, various types of epitaxial substrates 10 having different layer structures of the buffer layers 5 were produced. Table 1 shows the basic structure of the epitaxial substrate 10 of the embodiment, specifically, the formation materials and film thickness of each layer.
[0101] [Table 1]
[0102]
[0103] As shown in Table 1, in this embodiment, for all the extended substrates 10, the base substrate 1, the base layer 2 (the first base layer 2a and the second base layer 2b), and the functional layer 6 are made of the same material and film thickness formation. In addition, the functional layer 6 has a two-layer structure of a channel layer and a barrier layer.
[0104] On the other hand, both the first composition layer 31 and the terminal layer 4 are formed of AlN, but the film thickness differs depending on the sample. In Table 1, the film thicknesses of the first composition layer 31 and the terminal layer 4 are represented by the variable A (nm). ...
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Abstract
Provided is an epitaxial substrate which includes a silicon substrate as a base substrate and which is free from cracks and has excellent withstand voltage. The epitaxial substrate comprises: a base substrate which is single-crystal silicon having (111) orientation; and Group-III element nitride layers formed over the base substrate so that the (0001) crystal plane is approximately parallel to the surface of the base substrate. The epitaxial substrate includes a buffer layer comprising a composition modulation layer and a crystal layer formed on the buffer layer, the composition modulation layer being formed by alternately superposing a first composition layer constituted of AlN and a second composition layer constituted of AlxGa1-xN (0<=x<1), so as to satisfy the relationships x(1)>=x(2)>= ... >= x(n-1)>=x(n) and x(1)>x(n) where n (n is a natural number of 2 or larger) indicates the number of the superposed first composition layers and the number of the superposed second composition layers and the value of x in the i-th second composition layer from the base substrate side is expressed by x(i). Thus, the composition modulation layer has compression strain therein so that the farther from the base substrate, the larger the compression strain.
Description
[0001] The present invention relates to an epitaxial substrate for a semiconductor element, and more particularly, to an epitaxial substrate composed of a group III nitride. Background technique [0002] Nitride semiconductors are used as light-emitting devices such as LEDs and LDs, or as high-frequency / high-power devices such as HEMTs (High Electron Mobility Transistor) due to their direct-migration wide band gap, high dielectric breakdown electric field, and high saturation electron velocity. Semiconductor materials for electronic devices have attracted attention. For example, a HEMT (High Electron Mobility Transistor) element in which a barrier layer composed of AlGaN and a channel layer composed of GaN are stacked is an element that utilizes the following characteristics: due to the strong polarization effect (spontaneous polarization) peculiar to nitride materials effect and piezoelectric polarization effect) to generate high-concentration two-dimensional electron gas (2D...
Claims
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IPC IPC(8): H01L21/205C30B29/38H01L21/338H01L29/778H01L29/812
CPCH01L29/7786H01L21/02458C30B29/403H01L21/02507H01L21/02494H01L21/02516H01L21/0262H01L29/2003H01L21/02609H01L29/872H01L29/1075H01L29/155H01L21/0254C30B25/183H01L21/02381
Inventor 三好实人角谷茂名市村干也前原宗太田中光浩
Owner NGK INSULATORS LTD