GaN Drift Layer Carbon Gettering for Breakdown Voltage
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Solution Overview
Problem
Conventional power electronics face challenges in achieving precise control of dopant density in semiconductor devices, particularly in high voltage GaN devices, leading to limitations in breakdown voltage and device performance due to background carbon incorporation during epitaxial growth.
Innovation Solution
The method involves growing III-nitride-based epitaxial structures using a substrate in an epitaxial growth reactor, with a gettering gas like indium to reduce carbon incorporation, allowing for precise control of dopant concentration and achieving low resistivity and high breakdown voltages in vertical drift layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional epitaxial growth is used to grow thick vertical drift layers, then the drift layer thickness can be increased for high voltage operation, but background carbon incorporation increases leading to higher dopant concentrations and reduced breakdown voltage
Solution Approach 1:
A carbon getter layer comprising silicon is introduced as an intermediary between the substrate and the drift layer during epitaxial growth. This getter layer absorbs and traps carbon impurities, preventing their incorporation into the drift layer. The getter layer is positioned at a specific depth (50-200 nm from the substrate surface) and has controlled thickness (50-500 nm) to optimize carbon removal while maintaining dopant concentration control in the drift layer
Solution Approach 2:
The patent modifies the epitaxial growth process parameters by introducing the getter layer at specific growth stages and controlling its thickness and composition. By adjusting the getter layer parameters (thickness, composition, position) and growth conditions (temperature, pressure, gas flow), the patent achieves precise control over carbon incorporation and dopant concentration in the drift layer, enabling thick layers with low background doping
2Manufacturing precision
If background carbon concentration is reduced through gettering, then dopant concentration control precision improves, but the process complexity increases due to additional gettering gas flow requirements
Solution Approach 1:
The patent uses a carbon getter layer as an intermediary mechanism that passively removes carbon impurities during the epitaxial growth process. Rather than requiring complex real-time monitoring and adjustment systems, the getter layer continuously absorbs carbon as it is introduced, simplifying the control strategy while achieving precise dopant concentration control
Solution Approach 2:
The getter layer is prepared and positioned in advance before drift layer growth begins. By pre-establishing the carbon trapping mechanism, the system eliminates the need for complex dynamic control during growth, reducing process complexity while maintaining high precision dopant control
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 enables the fabrication of high voltage semiconductor devices with lower resistance and capacitance, allowing for more efficient power handling and increased reliability by reducing carbon background levels and improving dopant control, resulting in superior performance compared to conventional devices.
Implementation Method 1
flowing a gettering gas into the epitaxial growth reactor
Data Source
AI summary
A method of growing a III-nitride-based epitaxial structure is disclosed. The method includes forming a GaN-based drift layer coupled to the GaN-based substrate, where forming the GaN-based drift layer comprises doping the drift layer with indium to cause the indium concentration of the drift layer to be less than about 1×1016 cm−3 and to cause the carbon concentration of the drift layer to be less than about 1×1016 cm−3. The method also includes forming an n-type channel layer coupled to the GaN-based drift layer, forming an n-contact layer coupled to the GaN-based drift layer, and forming a second electrical contact electrically coupled to the n-contact layer.