Nitride Semiconductor Layer Polarity Control
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Solution Overview
Problem
Current nitride semiconductor light emitting devices face challenges in achieving superior quality semiconductor layers due to differences in surface polarity, leading to defects and degraded surface characteristics, particularly with N-polarity regions which result in hillocks, columns, or pyramids during re-growth, affecting crystalline and electrical properties.
Innovation Solution
A method is developed to fabricate nitride semiconductor light emitting devices by growing a first group III nitride semiconductor layer with a group III rich surface and a N-rich surface, selectively etching the N-polarity region using a KOH solution, and forming a second group III nitride semiconductor layer to fill the etched region, resulting in a light emitting structure with improved surface flatness and electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If N-polarity region is present in the top surface of the first group III nitride semiconductor layer, then the layer can be grown with both group III rich and N-rich surfaces, but the surface morphology degrades with hillocks, columns, or pyramids during re-growth
Solution Approach 1:
The N-polarity region is selectively removed from the top surface of the first group III nitride semiconductor layer through chemical etching. This extraction of the problematic N-polarity region eliminates the cause of surface degradation while preserving the group III rich surface, thereby resolving the contradiction between maintaining composition stability and achieving surface flatness
Solution Approach 2:
The patent applies different treatments to different regions of the semiconductor layer: the N-polarity region is selectively etched away while the group III rich surface is preserved. This local differentiation allows the structure to have optimal properties in different areas, resolving the contradiction by eliminating the harmful N-polarity regions while maintaining the beneficial group III rich surfaces
2Ease of manufacture
If N-polarity region is present in the semiconductor layer, then the layer structure is complete, but dislocation and defects increase affecting crystalline and electrical properties
Solution Approach 1:
The N-polarity region is selectively extracted through chemical etching using KOH solution. This removal eliminates the source of dislocation and defects that would otherwise compromise crystalline and electrical properties, while the subsequent formation of the second group III nitride semiconductor layer maintains structural completeness
Solution Approach 2:
The problematic N-polarity region is discarded through selective etching, and the resulting etched region is recovered by forming a second group III nitride semiconductor layer that fills the etched area. This process eliminates defects while restoring structural integrity, resolving the contradiction between manufacturing ease and reliability
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 enhances the quality of semiconductor layers by reducing dislocation and improving surface morphology, leading to superior crystalline and electrical characteristics, as evidenced by reduced full width at half maximum (FWHM) in X-ray diffraction values and improved etching characteristics.
Implementation Method 1
The etching of the N-polarity region may be performed by chemical wet etching. The chemical wet etching may be performed using a KOH solution having a concentration of 10% to 50%. The chemical wet etching may be performed at 60° C. to 100° C. within an hour.
Implementation Method 2
forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer so as to fill the etched N-polarity region
Implementation Method 3
as evidenced by reduced full width at half maximum (FWHM) in X-ray diffraction values
Data Source
AI summary
A method of fabricating a nitride semiconductor light emitting device is provided. The method includes growing a first group-III-nitride semiconductor layer on a substrate, the first group-III-nitride semiconductor layer having a top surface formed as a group-III-rich surface exhibiting a group-III-polarity and a bottom surface formed as a N-rich surface exhibiting a N-polarity. The method further includes selectively etching a N-polarity region in the top surface of the first group III nitride semiconductor layer, forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer to fill the etched N-polarity region and forming a light emitting structure including first and second conductivity type nitride semiconductor layers and an active layer on the second group III nitride semiconductor layer.