GaN Epitaxial Substrate Off-Angle for Low E3 Trap Uniformity
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Solution Overview
Problem
The challenge is to suppress high and low levels of E3 trap concentration and variations in the GaN layer of epitaxial substrates, as high E3 trap concentrations deteriorate semiconductor device properties and existing methods fail to maintain low and uniform E3 trap concentrations effectively.
Innovation Solution
An epitaxial substrate with a GaN layer grown on a GaN substrate, where the main surface has an off-angle of 0.4° or more, resulting in an E3 trap concentration of 3.0×10^13 cm^-3 or less and a ratio of maximum to minimum E3 trap concentration of 1.5 times or less, achieved through controlled crystal growth using methods like Void-assisted Separation Method and Metalorganic vapor phase epitaxy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional epitaxial growth methods are used on c-plane GaN substrates, then GaN layers can be grown, but E3 trap concentration becomes high and varies significantly
Solution Approach 1:
The patent changes the off-angle parameter of the c-plane substrate from conventional small angles to specifically 0.4° or more. This parameter change in substrate orientation fundamentally alters the epitaxial growth conditions, resulting in suppressed E3 trap concentration (3.0×10^13 cm^-3 or less) and reduced variation (ratio of max to min concentration of 1.5 times or less).
Solution Approach 2:
The patent applies preliminary action by pre-setting the substrate off-angle to 0.4° or more before epitaxial growth begins. This preliminary configuration of the substrate orientation ensures that subsequent GaN layer growth automatically occurs under conditions that suppress E3 trap formation, preventing the problem rather than correcting it after growth.
2Reliability
If carbon concentration in GaN layer is reduced to improve material quality, then device performance improves, but E3 trap concentration increases
Solution Approach 1:
The patent changes the substrate off-angle parameter to 0.4° or more, which fundamentally alters the growth dynamics. This parameter change enables the system to achieve low E3 trap concentration even when carbon concentration is reduced, breaking the conventional inverse relationship between carbon content and E3 trap formation.
Solution Approach 2:
The substrate off-angle acts as an intermediary parameter that mediates between carbon concentration and E3 trap formation. By optimizing this intermediate parameter (off-angle ≥ 0.4°), the patent enables independent control of carbon content and E3 trap concentration, allowing low carbon concentration without necessarily increasing E3 traps.
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
The approach effectively suppresses high and low levels of E3 trap concentration and variations, enhancing the properties of semiconductor devices by maintaining a low E3 trap concentration and high in-plane uniformity of the GaN layer.
Implementation Method 1
a GaN layer epitaxially grown on the main surface
Data Source
AI summary
There is provided an epitaxial substrate, including: a GaN substrate whose main surface is a c-plane; and a GaN layer epitaxially grown on the main surface, wherein the main surface includes a region where an off-angle is 0.4° or more, and an E3 trap concentration in the GaN layer grown on the region is 3.0×1013 cm−3 or less.