GaN Transistor Back Electrode Biasing for Current Collapse Reduction
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Solution Overview
Problem
Conventional power converters using silicon-based devices face limitations in reducing on-state resistance and switching speed, leading to insufficient reduction in current collapse and power conversion efficiency, despite the potential of GaN transistors.
Innovation Solution
A power converter design incorporating a GaN transistor with a back electrode configuration that reduces the potential difference between the back electrode and drain electrode in the off-state and applies a positive voltage bias to the back electrode in the on-state, minimizing current collapse and exploiting the low on-state resistance of the GaN transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaN transistor is formed on a conductive substrate with the source electrode penetrating to connect to the substrate, then the field plate effect is utilized to reduce current collapse, but the inherent low on-state resistance is not fully exploited and current collapse reduction is insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the potential of the back electrode relative to the source electrode. Specifically, the back electrode is set at a higher potential than the source electrode, creating a potential difference that optimizes both current collapse reduction and on-state resistance characteristics. This parameter adjustment allows the device to achieve low on-state resistance while maintaining reduced current collapse effects.
2Ease of operation
If the source electrode and conductive substrate have the same potential, then the conductive substrate functions as a field plate, but the low on-state resistance of the GaN transistor is not fully exploited
Solution Approach 1:
The patent implements dynamics by making the potential relationship between the back electrode and source electrode adjustable rather than fixed. The back electrode potential can be dynamically controlled to be higher than the source electrode potential, allowing the device to adapt between field plate functionality and optimal on-state resistance performance. This dynamic potential control enables both functions to coexist effectively.
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 configuration effectively reduces current collapse and enhances power conversion efficiency by minimizing electron trapping and discharge, resulting in a highly efficient power converter with reduced size and complexity.
Implementation Method 1
charge occurs at the heterojunction interface between aluminum gallium nitride (AlGaN) and gallium nitride (GaN) due to spontaneous polarization and piezoelectric polarization
Implementation Method 2
charge occurs at the heterojunction interface between aluminum gallium nitride (AlGaN) and gallium nitride (GaN) due to spontaneous polarization and piezoelectric polarization
Implementation Method 3
a two-dimensional electron gas (2DEG) layer is formed which has a sheet carrier concentration of 1×1013 cm−2 or more and a mobility of as high as 1000 cm2V/sec or more
Implementation Method 4
when the GaN transistor is in the off-state, a potential difference between the back electrode and the drain electrode is reduced
Implementation Method 5
when the GaN transistor is in the on-state, a positive voltage bias is applied to the back electrode
Data Source
AI summary
A power converter includes an input terminal configured to be connected to a power supply, an output terminal, and a first switching element coupled between the input terminal and the output terminal. The first switching element includes a semiconductor multilayer structure formed on a substrate and made of a nitride semiconductor, a gate electrode formed on the semiconductor multilayer structure, a first and a second ohmic electrode, and a back electrode formed on a back surface of the substrate. A potential is supplied from the power supply connected to the input terminal to the back electrode so that a potential difference between the back surface and the second ohmic electrode is reduced. When the first switching element is in the on-state, a positive voltage bias is applied to the back electrode.