GaN HEMT Buffer Layer Potential Control for Current Collapse
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Solution Overview
Problem
GaN-based high electron mobility transistors (HEMTs) experience current collapse and increased on-resistance during high voltage switching due to fluctuations in the electric potential of the semiconductor layer neighboring the substrate, leading to potential device breakdown.
Innovation Solution
A GaN-based semiconductor element with a buffer layer that includes an electro-conductive semiconductor layer, where the electric potential is controlled using electrodes or metal materials implanted into the epitaxial layer to reach the buffer layer, allowing for ohmic contact and stabilization of the electric potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high resistance buffer layer is used to reduce leakage current, then the withstand voltage is improved, but the on-resistance increases and current collapse occurs during high voltage switching
Solution Approach 1:
The buffer layer is divided into multiple regions with different resistance characteristics: a high resistance region for reducing leakage current and improving withstand voltage, and a low resistance region for preventing current collapse during switching. This segmentation allows simultaneous optimization of both contradictory requirements.
Solution Approach 2:
Different regions of the buffer layer are assigned different electrical properties (resistance values) based on their functional requirements. The first buffer layer region has high resistance to block leakage, while the second buffer layer region has low resistance to maintain stable potential during switching operations.
2Device complexity
If the electric potential of the buffer layer is not controlled, then the structure is simpler, but current collapse occurs due to potential fluctuations during high voltage switching
Solution Approach 1:
The buffer layer structure itself provides potential stabilization through its inherent low resistance region, eliminating the need for external control circuits or additional components. The structure serves its own stabilization function, maintaining simple overall device architecture while achieving reliable current collapse suppression.
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 solution effectively suppresses current collapse and increases the withstand voltage, reducing leakage current and preventing device breakdown, enabling the use of GaN-based transistors in high voltage applications with low leakage current.
Implementation Method 1
a part or whole of the buffer layer is formed to be an electro-conductive semiconductor layer
Implementation Method 2
a structure to control an electric potential of the electro-conductive semiconductor layer is included... a part of electrodes or a part of metal materials implanted into the epitaxial layer to be extended to a depth reaching the buffer layer for ohmic contacting to the buffer layer
Data Source
AI summary
A GaN-based semiconductor element includes a substrate, a buffer layer formed on the substrate, including an electrically conductive portion, an epitaxial layer formed on the buffer layer, and a metal structure in ohmic contact with the electrically conductive portion of the buffer layer for controlling an electric potential of the buffer layer.