GaN Substrate Reuse via Band-Gap-Selective PEC Etching
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Solution Overview
Problem
The high cost of bulk GaN substrates limits the widespread adoption of high-quality GaN devices due to the lack of methods for reusing these expensive substrates, which are typically damaged during removal processes, leading to increased device production costs.
Innovation Solution
The use of band-gap-selective photoelectrochemical (PEC) etching to nondestructively remove epitaxial layers from bulk GaN substrates, allowing the substrates to be reused for further growth without damaging the substrate, thereby reducing the cost of device production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If traditional removal processes are used to separate epitaxial layers from GaN substrates, then the epitaxial layers can be removed, but the substrates are damaged and cannot be reused, leading to increased device production costs
Solution Approach 1:
The patent introduces a sacrificial layer with distinct material properties (different etch selectivity) that segments the substrate structure into separable components. This sacrificial layer acts as a temporary intermediary that can be selectively removed, separating the epitaxial device layers from the substrate without damaging either component, thereby enabling substrate reuse and reducing production costs
Solution Approach 2:
The sacrificial layer serves as an intermediary element between the substrate and the epitaxial layers. This intermediary layer facilitates the separation process by providing a selective etching target that allows clean detachment of the epitaxial structure from the substrate, preserving both the substrate for reuse and the epitaxial layers for device fabrication
2Reliability
If bulk GaN substrates are used instead of heteroepitaxial substrates, then device performance and crystal quality are improved, but the substrate cost increases significantly
Solution Approach 1:
The patent enables the recovery and reuse of expensive bulk GaN substrates through the sacrificial layer separation technique. Instead of discarding substrates after single-use heteroepitaxial growth, the sacrificial layer method allows substrates to be recovered intact and reused multiple times, significantly reducing the effective cost per device while maintaining the performance benefits of bulk GaN substrates
3Ease of manufacture
If substrates are removed and reused, then production cost decreases, but substrate integrity and crystal quality may be compromised
Solution Approach 1:
The patent extracts only the necessary component (the sacrificial layer) for the separation process, leaving the substrate and epitaxial layers intact. By selectively removing only the sacrificial material through targeted etching, the substrate crystal quality is preserved without compromise, enabling multiple reuse cycles while maintaining manufacturing precision
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 method enables the reuse of GaN substrates multiple times, significantly reducing the per-device cost of GaN-based electronic and optoelectronic devices by maintaining the substrate's integrity and crystal quality, similar to new substrates, and allowing for the growth of high-performance devices without performance degradation.
Implementation Method 1
The method comprises performing an etch to remove one or more epitaxial layers from a bulk or free-standing GaN or III-nitride substrate, without damaging the substrate, thereby allowing the substrate to be reused for further growth of additional epitaxial layers
Implementation Method 2
The use of band-gap-selective photoelectrochemical (PEC) etching to nondestructively remove epitaxial layers from bulk GaN substrates
Data Source
AI summary
A method for the reuse of gallium nitride (GaN) epitaxial substrates uses band-gap-selective photoelectrochemical (PEC) etching to remove one or more epitaxial layers from bulk or free-standing GaN substrates without damaging the substrate, allowing the substrate to be reused for further growth of additional epitaxial layers. The method facilitates a significant cost reduction in device production by permitting the reuse of expensive bulk or free-standing GaN substrates.