GaN Diode Dislocation Density Control via ELO Masking
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Solution Overview
Problem
Structural defects in GaN-based electronic devices limit their performance and reliability, necessitating improved methods to control defect density, particularly in high voltage devices with vertical current flow.
Innovation Solution
The application of epitaxial lateral overgrowth (ELO) techniques to reduce dislocation density, combined with optimized device geometry, such as stripe-shaped Schottky barrier diodes and p-n junction diodes aligned with ELO masks, to create regions of high-quality epitaxial material suitable for high power applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GaN-based electronic devices are used, then device complexity is reduced, but dislocation density is high leading to limited performance and reliability
Solution Approach 1:
The device structure is segmented into distinct regions with different dislocation densities through the masking layer. The masking layer creates separate high-field regions (over continuous sections with reduced dislocation density) and other functional regions, allowing each segment to be optimized for its specific function while managing defect distribution.
Solution Approach 2:
The patent applies local quality by creating regions of locally reduced defect densities through the ELO process. The masking layer with continuous sections and openings produces spatially varying dislocation densities, enabling high-field regions to be positioned precisely where low dislocation density is critical for device reliability and performance.
2Reliability
If ELO techniques with masking layers are applied to reduce dislocation density, then reliability improves, but device complexity increases
Solution Approach 1:
The masking layer is formed preliminarily before the epitaxial growth process. By pre-configuring the masking layer with continuous sections and openings on the substrate, the subsequent ELO process automatically produces the desired dislocation density distribution, simplifying the overall manufacturing approach while achieving complex defect engineering.
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 significantly reduces dislocation density, enhancing the performance and reliability of GaN-based electronic devices by positioning high field regions over areas with locally reduced defect densities, resulting in improved electrical characteristics and device operation.
Implementation Method 1
performing an epitaxial lateral overgrowth process to form a III-nitride epitaxial layer greater than 5 μm in thickness coupled to the substrate and the masking layer
Data Source
AI summary
A diode includes a substrate characterized by a first dislocation density and a first conductivity type, a first contact coupled to the substrate, and a masking layer having a predetermined thickness and coupled to the semiconductor substrate. The masking layer comprises a plurality of continuous sections and a plurality of openings exposing the substrate and disposed between the continuous sections. The diode also includes an epitaxial layer greater than 5 μm thick coupled to the substrate and the masking layer. The epitaxial layer comprises a first set of regions overlying the plurality of openings and characterized by a second dislocation density and a second set of regions overlying the set of continuous sections and characterized by a third dislocation density less than the first dislocation density and the second dislocation density. The diode further includes a second contact coupled to the epitaxial layer.