HEMT Control Electrode Biasing for Current Collapse Reduction
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Solution Overview
Problem
High electron mobility transistors (HEMTs) experience current collapse when transitioning from an off-state to an on-state due to trapped electrons in the channel supply layer, leading to increased resistance and accelerated degradation.
Innovation Solution
Applying a control voltage to a control electrode, electrically separated from the source, drain, and gate electrodes, with a negative control voltage to detrapped electrons before applying a gate voltage, and a positive control voltage to enhance electron distribution, reduces current collapse by moving trapped electrons to a depletion region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage is applied to the drain electrode to turn off the HEMT, then the transistor can be effectively turned off, but electrons are trapped in the channel supply layer causing current collapse when turning on
Solution Approach 1:
A control electrode is introduced as an intermediary element between the gate electrode and the channel supply layer. This control electrode independently manages electron trapping and detrapping processes, mediating the interaction between the gate voltage and the channel to prevent current collapse while maintaining effective switching.
Solution Approach 2:
The control electrode applies preliminary detrapping action before the gate voltage is applied to turn on the transistor. By removing trapped electrons in advance through the control electrode, the channel is prepared to conduct current properly when the gate voltage is applied, preventing current collapse.
2Device complexity
If trapped electrons are not removed, then the device structure remains simple, but on-resistance increases and current collapse occurs
Solution Approach 1:
The control electrode serves multiple functions: it prevents electron trapping during off-state, detraps electrons before on-state, and can independently control the channel without requiring modifications to the gate electrode or channel structure. This multi-functionality achieves reliable current conduction with minimal structural complexity.
3Power
If electrons are trapped in the channel supply layer, then the transistor can be turned off with high voltage, but heat generation increases due to increased resistance
Solution Approach 1:
The control electrode acts as a mediator that separates the power control function (drain voltage) from the electron management function (gate and control electrode voltages). This allows independent optimization of power control and electron distribution, preventing resistive heating caused by trapped electrons.
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 method effectively reduces current collapse and resistance in HEMTs, minimizing heat generation and degradation by ensuring electrons are properly distributed, thereby improving the device's operational efficiency.
Implementation Method 1
applying a control voltage to a control electrode of the power device, the control voltage being separately applied to the control electrode... detrapping the electrons trapped in the channel supply layer by applying a negative control voltage to the control electrode
Implementation Method 2
forming electrons on a lower side of the control electrode by applying a positive control voltage to the control electrode when the gate voltage is applied to the gate electrode
Data Source
AI summary
According to example embodiments, a method of operating a power device includes applying a control voltage to a control electrode of the power device, where the control electrode is electrically separated from a source electrode, a drain electrode, and a gate electrode of the power device. The control voltage is separately applied to the control electrode. The method may include applying a negative control voltage to the control electrode prior to applying a gate voltage to the gate electrode.