Continuous GaN PN Structure Eliminates Regrowth Defects
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Solution Overview
Problem
Conventional fabrication techniques for vertical GaN transistors result in high defect densities at PN junctions due to regrowth processes, leading to current leakages and low breakdown voltages, necessitating an efficient method to reduce or eliminate interface defects.
Innovation Solution
The development of continuous crystalline GaN PN structures with no internal regrowth interfaces, achieved through a precursor cell structure with a mask layer exposing specific areas for vertical and lateral growth of dopant regions, utilizing metal-organic chemical vapor deposition (MOCVD) or Hydride Vapor Phase Epitaxy (HVPE) and epitaxial lateral overgrowth (ELO) to minimize defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional regrowth techniques are used to fabricate GaN PN junctions, then the manufacturing process can be completed, but high defect densities are introduced at the PN junction interfaces
Solution Approach 1:
The patent extracts and eliminates the harmful regrowth interface from the fabrication process. By using a single continuous epitaxial growth step to form both the drift region and control region without intermediate etching or cleaning, the problematic regrowth interface is completely removed, preventing defect formation at the PN junction
Solution Approach 2:
The patent implements continuous epitaxial growth to form the GaN PN structure. The drift region and control region are grown in a single continuous process without interruption, maintaining continuous crystalline growth and avoiding the formation of defective regrowth interfaces that would otherwise occur with conventional regrowth techniques
2Ease of manufacture
If regrowth processes are used to create PN junctions, then the device structure can be formed, but current leakages increase due to interface defects
Solution Approach 1:
The patent removes the harmful regrowth interface that causes current leakage paths. By using continuous epitaxial growth without intermediate processing steps, the source of leakage (the regrowth interface) is extracted from the device structure, resulting in improved reliability and reduced current leakage
Solution Approach 2:
The patent converts the potential harm of interface formation into a benefit by using continuous growth. Instead of creating an interface through regrowth (which causes defects), the method uses a single growth process where the interface is formed without disruption, turning what would be a harmful discontinuity into a beneficial continuous structure
3Ease of manufacture
If regrowth processes are used to fabricate GaN devices, then the doping regions can be created, but breakdown voltages decrease due to interface damage
Solution Approach 1:
The patent uses continuous epitaxial growth to create both the drift region and control region in a single uninterrupted process. This continuous action maintains the integrity of the crystalline structure and avoids the damage that would occur with regrowth, resulting in higher breakdown voltages while still achieving the required doped region creation
4Adaptability or versatility
If multiple regrowth steps are used, then complex device structures can be achieved, but manufacturing efficiency decreases
Solution Approach 1:
The patent merges multiple separate regrowth steps into a single continuous epitaxial growth process. By combining the formation of the drift region and control region into one uninterrupted growth step, the method reduces manufacturing time and increases efficiency while still achieving the complex doped region structure required for vertical GaN transistors
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 reduces regrowth-related defects, enhancing the reliability and efficiency of GaN-based transistors by minimizing current leakages and increasing breakdown voltages, resulting in more robust high-power devices.
Implementation Method 1
utilizing metal-organic chemical vapor deposition (MOCVD) or Hydride Vapor Phase Epitaxy (HVPE)
Implementation Method 2
utilizing metal-organic chemical vapor deposition (MOCVD) or Hydride Vapor Phase Epitaxy (HVPE) and epitaxial lateral overgrowth (ELO)
Data Source
AI summary
A precursor cell for a transistor having a foundation structure, a mask structure, and a gallium nitride (GaN) PN structure is provided. The mask structure is provided over the foundation structure to expose a first area of a top surface of the foundation structure. The GaN PN structure resides over the first area and at least a portion of the mask structure and has a continuous crystalline structure with no internal regrowth interfaces. The GaN PN structure comprises a drift region over the first area, a control region laterally adjacent the drift region, and a PN junction formed between the drift region and the control region. Since the drift region and the control region form the PN junction having no internal regrowth interfaces, the GaN PN structure has a continuous crystalline structure with reduced regrowth related defects at the interface of the drift region and the control region.