Group-III Nitride Substrate Orientation for Blue Shift Suppression
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Solution Overview
Problem
Existing nitride semiconductor substrates with (0001) plane orientation suffer from significant blue shift in emission due to piezoelectric polarization, leading to lower emission intensity in light emitting devices, and there is a lack of clarity on suitable substrate plane orientation, surface roughness, and crystallinity for suppressing this blue shift.
Innovation Solution
A group III nitride crystal substrate with specific plane orientations, surface roughness, and crystallinity characteristics, including a plane orientation inclined between 10° and 80° relative to (0001) planes, a surface roughness of 3 nm or lower, and controlled distortions, is developed to suppress piezoelectric polarization and enhance emission intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If (0001) plane oriented nitride semiconductor substrate is used, then epitaxial growth is facilitated, but piezoelectric polarization causes significant blue shift and reduces emission intensity
Solution Approach 1:
The patent changes the plane orientation parameter of the substrate from (0001) to non-(0001) orientations (such as (10-10), (11-20), or mixed orientations). This parameter change eliminates piezoelectric polarization while maintaining epitaxial growth capability, thereby resolving the contradiction between ease of manufacture and emission intensity.
2Shape
If mechanical polishing is performed on GaN crystal, then surface flatness is improved, but process-induced degradation layer is formed
Solution Approach 1:
The patent extracts and removes the process-induced degradation layer formed by mechanical polishing through subsequent CMP or dry etching processes. This extraction approach allows the benefits of mechanical polishing (surface flatness) to be retained while eliminating the harmful degradation layer.
Solution Approach 2:
The patent introduces CMP or dry etching as an intermediary process between mechanical polishing and epitaxial growth. This intermediary step removes the degradation layer created by mechanical polishing, allowing the surface flatness benefits to be preserved while eliminating harmful effects.
3Manufacturing precision
If CMP processing is used to remove degradation layer, then surface quality is improved, but processing rate is low and cost increases
Solution Approach 1:
The patent performs preliminary mechanical polishing to achieve the required surface flatness before epitaxial growth, and uses selective CMP or dry etching only on specific areas or under specific conditions. This preliminary action approach reduces the overall CMP processing time and cost while maintaining surface quality.
4Object-generated harmful factors
If dry etching is used to remove degradation layer, then degradation layer is removed, but surface roughness increases
Solution Approach 1:
The patent applies different processing methods to different regions or stages: mechanical polishing for overall flatness, selective CMP or dry etching for degradation layer removal in specific areas, and final smoothing processes for surface roughness control. This local quality approach allows degradation layer removal while maintaining surface smoothness.
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 substrate effectively reduces blue shift and increases emission intensity in light emitting devices by optimizing substrate surface properties, leading to improved semiconductor device performance.
Implementation Method 1
suffer from significant blue shift in emission due to piezoelectric polarization
Implementation Method 2
the main surface of the substrate providing a base of epitaxial growth has a smooth form
Implementation Method 3
a plurality of nitride semiconductor layers (e.g., group III nitride semiconductor layers) are epitaxially grown on a substrate
Data Source
Figure 1~2
Figure 3(a)~4(b)
Figure 5(a)~6
AI summary
A group III nitride crystal substrate is provided in which, wherein, a plane spacing of arbitrary specific parallel crystal lattice planes of the crystal substrate being obtained from X-ray diffraction measurement performed with variation of X-ray penetration depth from a main surface (1s) of the crystal substrate while X-ray diffraction conditions of the specific parallel crystal lattice planes of the crystal substrate are satisfied, a uniform distortion at a surface layer of the crystal substrate represented by a value of |d1 - d2|/d2 obtained from a plane spacing d1 at the X-ray penetration depth of 0.3 µm and a plane spacing d2 at the X-ray penetration depth of 5 µm is equal to or lower than 1.9 x 10-3, and wherein the main surface (1s) has a plane orientation inclined in the <10-10> direction at an angle equal to or greater than 10° and equal to or smaller than 80° with respect to one of (0001) and (000-1) planes (1c) of the crystal substrate. A group III nitride crystal substrate suitable for manufacturing a light emitting device with a blue shift of an emission suppressed, an epilayer-containing group III nitride crystal substrate, a semiconductor device and a method of manufacturing the same can thereby be provided.