Semipolar Group III Nitride Substrate Growth via Polarity Control
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Solution Overview
Problem
The existing techniques for growing group III nitride semiconductor substrates with semipolar planes face challenges in maintaining excellent crystallinity as the thickness increases, particularly with Ga polar components, leading to worse X-ray rocking curve half widths and difficulties in obtaining bulk crystals with high quality.
Innovation Solution
A method involving the preparation of a sapphire substrate, heat treatment, pre-flow step, buffer layer formation, and subsequent growth of group III nitride semiconductor layers using MOCVD and HVPE methods, ensuring growth conditions that maintain N polarity and result in semipolar planes with improved crystallinity, achieving a difference in XRC half widths of 500 arcsec or less between top and bottom surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a group III nitride semiconductor layer is grown on a sapphire substrate with a semipolar plane having a Ga polar component as a growth plane, then the substrate can be manufactured with a semipolar plane orientation, but the half width of the X-ray rocking curve becomes worse as the thickness increases to 1 mm or more
Solution Approach 1:
The patent changes the polarity parameter of the growth plane from Ga polar component to N polar component. This parameter change fundamentally alters the growth characteristics, allowing thick substrates (1 mm or more) to maintain excellent crystallinity with narrow X-ray rocking curve half widths while still achieving the desired semipolar plane orientation.
2Volume of moving object
If the thickness of the group III nitride semiconductor substrate is increased to obtain bulk crystal, then the substrate can be used for high-power devices, but the crystallinity deteriorates with conventional growth methods
Solution Approach 1:
The patent changes the growth plane polarity parameter to N polar component, which enables the growth of thick bulk crystals (1 mm or more) while maintaining excellent crystallinity. This parameter change allows simultaneous achievement of large thickness for high-power devices and high crystallinity for device performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the growth of bulk crystals with excellent crystallinity and semipolar plane substrates, enabling the production of high-quality free-standing substrates with large diameters and maintaining low XRC half widths across varying thicknesses, overcoming the limitations of previous methods.
Implementation Method 1
a heat treatment step of performing heat treatment on the sapphire substrate after the substrate preparation step
Implementation Method 2
a pre-flow step of supplying a metal-containing gas onto the sapphire substrate after the heat treatment step
Implementation Method 3
a buffer layer forming step of forming a buffer layer over the sapphire substrate under growth conditions of a growth temperature of 800° C. or higher and 950° C. or lower and a pressure of 30 torr or higher and 200 torr or lower
Implementation Method 4
a first growth step of forming a first growth layer by growing a group III nitride semiconductor over the buffer layer under growth conditions of a growth temperature of 800° C. or higher and 1025° C. or lower, a pressure of 30 torr or higher and 200 torr or lower, and a growth rate of 10 μm/h or higher using an MOCVD method
Implementation Method 5
a second growth step of forming a second growth layer by growing a group III nitride semiconductor over the first growth layer using an HVPE method
Data Source
AI summary
There is provided a group III nitride semiconductor substrate (free-standing substrate (30)) that is formed of a group III nitride semiconductor crystal and has a thickness of 300 μm or more and 1000 μm or less. Both exposed first and second main surfaces in a relationship of top and bottom are semipolar planes. A difference in a half width of an X-ray rocking curve (XRC) measured by making X-rays incident on each of the first and second main surfaces in parallel to an m axis of the group III nitride semiconductor crystal is 500 arcsec or less.