InGaN Epitaxial Reference Electrode for Stable Solid-State Sensing
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Solution Overview
Problem
Existing electrochemical sensors lack stable, all-solid-state reference electrodes, leading to issues such as bulkiness, difficulty in miniaturization, limited lifetime, and cumbersome maintenance of liquid-filled Ag/AgCl electrodes, and insufficient stability of solid-state alternatives.
Innovation Solution
A reference electrode using an InGaN-based semiconductor heterostructure with an InGaN layer (20-60% In content) and an InN layer (0.5-1.5 monolayers) to provide a stable, solid-state structure that maintains a constant electric potential independent of solution concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reference electrodes are used, then electrochemical measurements can be performed, but the electrodes are fragile, have limited lifetime, and require frequent replacement
Solution Approach 1:
The patent creates a solid-state copy of the reference electrode function using an epitaxial semiconductor wafer. Instead of using a conventional liquid-filled reference electrode with fragile components, the invention replicates the reference electrode's electrochemical function through a solid semiconductor structure with controlled doping regions that provide stable reference potential without mechanical fragility.
Solution Approach 2:
The patent changes the physical and chemical parameters of the reference electrode by transitioning from liquid/electrolyte-based conventional electrodes to a solid-state epitaxial semiconductor structure. The controlled doping concentrations and thermal diffusion processes create specific electrical properties that provide stable reference potential with enhanced durability and extended lifetime.
2Adaptability or versatility
If conventional electrochemical sensors are used, then chemical analysis can be performed, but the sensors lack integration with microelectronic processing and require separate handling
Solution Approach 1:
The patent merges the electrochemical sensor function with microelectronic processing by fabricating the reference electrode and sensor elements on a common epitaxial semiconductor wafer. This integration allows both electrochemical sensing and electronic signal processing to coexist on the same substrate, enabling combined chemical and electrical analysis capabilities within a single device platform.
Solution Approach 2:
The epitaxial semiconductor wafer serves multiple functions simultaneously: it provides the reference electrode structure, contains the working electrode for electrochemical sensing, and integrates with microelectronic circuitry for signal processing. This multi-functional platform eliminates the need for separate handling of electrochemical and electronic components.
3Reliability
If traditional reference electrode structures are used, then reference potential can be established, but the electrodes require frequent maintenance and replacement
Solution Approach 1:
The patent replaces expensive, fragile conventional reference electrodes with a durable solid-state epitaxial semiconductor structure that eliminates the need for frequent replacement. The solid-state construction with controlled doping profiles provides long-term stability without the maintenance issues associated with liquid electrolyte-based electrodes, effectively creating a permanent rather than disposable solution.
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 InGaN-based reference electrode achieves a stable electrochemical response with minimal drift (less than 5 mV/decade concentration change and 1 mV/hour drift) and eliminates the need for liquid-filled electrodes, enhancing sensor stability and compactness.
Implementation Method 1
the n-type diffused region can be used as a reference electrode
Implementation Method 2
the p-type diffused region can serve as an electrochemical sensor
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
Disclosed are an epitaxial wafer and a method of fabricating the same, and an electrochemical sensor, wherein the reference electrode comprises: a substrate (11); an InGaN layer (12) formed on a surface of the substrate (11) and having an In content between 20% and 60% so as to ensure that a transition from negatively charged surface states to positively charged surface states occurs within a composition range; and an InN layer (13) formed on a surface of the InGaN layer (12) facing away from the substrate (11) to act as a stabilization layer. The InGaN layer (12) with an In content between 20% and 60% allows generation of an electrochemical response independent of the concentration of a solution to be detected; and in addition, the InN layer (13) with a high density of intrinsic, positively charged surface states further improves the electrochemical stability of the reference electrode, and the combination of the InGaN layer (12) and the InN layer (13) further enables the reference electrode which is made of the epitaxial wafer to have a stable electrochemical response.