Bidirectional power transistor and method for producing a bidirectional power transistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bidirectional power transistors based on gallium nitride have low threshold voltages, which are insufficient for preventing parasitic connections in safety-critical applications due to low charge carrier density in two-dimensional electron gas.
Innovation Solution
The bidirectional power transistor features an AlGaN/GaN structure with slanting sidewalls for the gate structures, which increases the threshold voltage by locally depleting the charge carrier density, and can be produced using a method involving epitaxy and p-doped regions on undoped GaN layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bidirectional power transistors are produced using lateral high-electron mobility transistors, then the transistor can conduct and block in two directions with low closing resistances and high break-through voltages, but the threshold voltage is too low (fewer than 1.5 V) to reliably prevent parasitic connections
Solution Approach 1:
The patent introduces a depression structure with slanting sidewalls at the gate location, creating a localized region with different charge carrier density characteristics. This local structural modification depletes the two-dimensional electron gas more effectively at the gate, increasing the threshold voltage specifically where needed for switching control, without affecting other regions of the transistor
Solution Approach 2:
The patent transitions from a planar gate structure to a three-dimensional depression structure with slanting sidewalls. This dimensional change allows the gate to extend into the vertical dimension, increasing its control over the channel and enhancing the depletion effect, thereby raising the threshold voltage to levels suitable for preventing parasitic connections
2Reliability
If the charge carrier density in two-dimensional electron gas is increased to improve conductivity, then the transistor conducts better, but the threshold voltage decreases making it unable to prevent parasitic connections
Solution Approach 1:
The depression structure creates a localized region with reduced charge carrier density at the gate area. By concentrating the depletion effect in this specific local region, the patent achieves higher threshold voltage control without requiring overall reduction of charge carriers in the entire device, maintaining good conductivity in active regions while enabling reliable switching control
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 design enhances the threshold voltage, ensuring reliable operation in both directions and suitable for safety-critical applications by requiring a higher gate voltage to activate conductivity, thus preventing parasitic connections.
Implementation Method 1
the charge carrier density within the two-dimensional electron gas is lowered locally so that the threshold voltage is increased
Implementation Method 2
applying an undoped AlGaN layer to the undoped GaN layer with the aid of epitaxy
Data Source
AI summary
A bidirectional power transistor. The bidirectional power transistor has an AlGaN/GaN structure, a first gate structure and a second gate structure. A surface of the AlGaN/GaN structure has a depression having a first slanting sidewall and a second slanting sidewall. The depression has a width that is greater than a height of the depression. The first gate structure is situated on the first slanting sidewall and the second gate structure is situated on the second slanting sidewall.