Enhancement-mode HEMT with Spaced-apart Gate Electrodes
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face challenges in managing voltage overshoot during reverse conduction without causing further complications, as they lack a pn junction diode present in Si MOSFETs, leading to increased power dissipation and potential gate bounce issues.
Innovation Solution
The design incorporates spaced-apart gate electrodes with a continuous depletion region in the off-state, allowing reverse conduction along a heterojunction below the space, reducing the area of reverse conduction and power dissipation, and optionally includes a smaller transistor or diode with source and gate electrically connected to form a barrier diode for preferential reverse conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If HEMT lacks a pn junction diode like Si MOSFET, then the device structure is simpler, but voltage overshoot cannot be dissipated effectively causing increased power dissipation
Solution Approach 1:
The gate electrode is divided into multiple spaced-apart gate electrodes, creating multiple depletion regions that work together to enable reverse conduction while maintaining a simpler overall device structure without requiring a pn junction diode
Solution Approach 2:
A barrier diode structure is introduced as an intermediary component to facilitate reverse conduction and dissipate voltage overshoot, solving the power dissipation problem without complicating the main HEMT structure
2Loss of energy
If spaced-apart gate electrodes are used to enable reverse conduction, then power dissipation is reduced, but gate bounce issues may occur
Solution Approach 1:
The width of the spaces between gate electrodes is optimized to a specific range to balance reverse conduction performance with gate bounce suppression, changing the geometric parameters to achieve both goals simultaneously
Solution Approach 2:
Different regions of the gate structure have different properties - the spaced-apart gate electrodes create localized depletion regions with specific characteristics that enable reverse conduction while the overall configuration maintains gate stability
3Reliability
If a barrier diode is added for preferential reverse conduction, then reverse conduction control is improved, but device complexity increases
Solution Approach 1:
The barrier diode is merged with the HEMT structure by sharing common source and drain electrodes, allowing reverse conduction control to be achieved without adding completely separate components and minimizing overall device complexity
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 significantly reduces power dissipation during reverse conduction, with the power dissipated being approximately 9% of conventional designs, and minimizes gate bounce by controlling the width of the spaces between gate electrodes.
Implementation Method 1
the first space has a width configured such that a continuous depletion region forms across all of the width of the first space
Implementation Method 2
reverse conduction occurs along a heterojunction below the space
Data Source
AI summary
An electronic device can include an enhancement-mode high electron mobility transistor (HEMT) that includes a source electrode; a drain electrode; and a gate. In an embodiment, the gate can correspond to spaced-apart gate electrodes and a space disposed between the spaced-apart gate electrodes, wherein the first space has a width configured such that, a continuous depletion region forms across all of the width of the first space. In another embodiment, the gate can be a gate electrode having a nonuniform thickness along a line in a gate width direction. In another aspect, a method of using the electronic device can include, during a transient period when the HEMT is in an off-state, flowing current from the drain electrode to the source electrode when Vds>−Vth+Vgs.