AlN Buffer Layer Leakage Current Reduction in GaN-on-Si Devices
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Solution Overview
Problem
Conventional semiconductor devices made of silicon have limited critical electric field and high resistance, leading to large and heavy devices operating at low frequencies, making them unsuitable for advanced applications like hybrid vehicles, and nitride semiconductor devices on silicon substrates face high leakage current and lower breakdown voltage due to the conductivity of the Si substrate.
Innovation Solution
A current blocking structure with p-n junctions or insulating regions is formed in the substrate to reduce leakage current and increase breakdown voltage, allowing for the growth of nitride semiconductor materials on silicon substrates while minimizing wafer bow and enhancing thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If GaN is grown on Si substrate, then cost is reduced and thermal conductivity is improved, but leakage current increases and breakdown voltage decreases
Solution Approach 1:
An AlN buffer layer is introduced as an intermediary between the GaN layer and the Si substrate. This buffer layer acts as a mediator that blocks leakage current paths while maintaining the low cost and high thermal conductivity advantages of the Si substrate. The AlN layer has high electrical resistance and forms a discontinuous barrier that prevents carrier leakage without requiring complete substrate removal.
Solution Approach 2:
The AlN buffer layer is formed with non-uniform thickness, being thicker in regions where leakage current is more problematic (such as under the gate and drain regions) and thinner in other areas. This local variation in buffer layer quality optimizes leakage blocking where needed while maintaining device performance and reducing overall buffer thickness.
2Ease of manufacture
If GaN is grown on Si substrate, then cost is reduced and thermal conductivity is improved, but breakdown voltage is reduced
Solution Approach 1:
The AlN buffer layer serves as an intermediary that modifies the electrical field distribution at the GaN-Si interface. By blocking leakage current paths, it prevents premature breakdown and allows the device to sustain higher voltages before breakdown occurs, thereby improving breakdown voltage while retaining the cost advantages of Si substrates.
3Strength
If epitaxial layer thickness is increased to improve breakdown voltage, then breakdown voltage increases, but wafer bow increases making fabrication difficult
Solution Approach 1:
Rather than uniformly increasing the epitaxial layer thickness across the entire wafer, the invention uses localized variations in AlN buffer layer thickness and composition to improve breakdown voltage in critical regions. This approach provides the necessary electrical strength without inducing excessive wafer bow that would complicate fabrication.
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 leakage current and increases breakdown voltage, enabling the production of high-performance power transistors suitable for hybrid vehicles, solar cell inverters, and LED power converters, with potential for larger wafer sizes and improved nitride material quality.
Implementation Method 1
a current blocking structure with p-n junctions or insulating regions is formed in the substrate to reduce leakage current
Data Source
AI summary
A semiconductor device includes a first region having a first semiconductor material and a second region having a second semiconductor material. The second region is formed over the first region. The semiconductor device also includes a current blocking structure formed in the first region between first and second terminals of the semiconductor device. The current blocking structure is configured to reduce current flow in the first region between the first and second terminals.