GaN HEMT Gate Control for Switching Time Reduction
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Solution Overview
Problem
The existing gate drive circuits for GaN based HEMTs face challenges in reducing switching time due to the injection of holes during conductivity modulation, which increases the on-resistance and prolongs the switching time of junction HEMTs.
Innovation Solution
A gate control device and method that control the gate voltage to maintain a state where the rate of time variation starts decreasing between the second and first threshold voltages when shutting down forward current, preventing hole injection and reducing switching time by maintaining the transistor in an on-state without hole injection for a predetermined time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hole injection is performed to achieve conductivity modulation, then on-resistance is reduced, but switching time increases
Solution Approach 1:
The gate voltage is preliminarily set to a value between the first and second threshold voltages before hole injection occurs. This preliminary voltage setting prevents excessive hole injection into the channel layer, thereby reducing the carrier lifetime extension that causes prolonged switching time, while still maintaining sufficient conductivity modulation to keep on-resistance low.
Solution Approach 2:
The invention changes the gate voltage parameter from conventional high voltage (above second threshold) to a specific intermediate range (between first and second threshold voltages). This parameter change optimizes the balance between conductivity modulation and carrier lifetime, achieving both low on-resistance and fast switching time simultaneously.
2Reliability
If gate voltage is increased to maintain transistor on-state, then conductivity is improved, but hole injection increases switching time
Solution Approach 1:
The gate voltage is optimized to a specific parameter range (between first and second threshold voltages) that provides sufficient conductivity modulation for stable on-state operation without causing excessive hole injection that would extend carrier lifetime and increase switching time.
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 effectively reduces the switching time of GaN based HEMTs by ensuring the hole in the channel layer disappears during the predetermined time, thereby shortening the overall switching time and preventing reverse recovery currents that could cause short circuits.
Implementation Method 1
injecting a positive hole (hole) from the gate electrode to a channel causes conductivity modulation
Implementation Method 2
A High Electron Mobility Transistor (HEMT) structure using a two dimensional electron gas (2DEG) as the carrier
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
A semiconductor device according to an embodiments controls a gate voltage to be applied to a gate electrode of a junction field effect transistor 10 including a source electrode 11, a drain electrode 12, and the gate electrode 13, the transistor having a first threshold voltage at which the transistor is turned on, and a second threshold at which conductivity modulation occurs in the transistor so as to make the gate voltage equal to or higher than the second threshold voltage when a forward current in a direction from the drain electrode toward the source electrode flows, and so as to make the time variation in gate voltage have a point from which the rate of the time variation starts decreasing at a voltage between the second threshold voltage and the first threshold voltage when the forward current to be shut down.