Normally-off Heterojunction Transistor with Reduced On-state Resistance
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Solution Overview
Problem
Widebandgap HEMTs, particularly gallium nitride-based transistors, face high on-state resistance issues due to their design, which affects their performance in high-power, high-frequency applications.
Innovation Solution
A normally-off heterojunction field-effect transistor design featuring a barrier layer and charge-trapping layer structure, with a two-dimensional electron gas formed at the interface, and a specific stack of n-type and p-type semiconductor layers to reduce on-state resistance and enhance breakdown voltage, including a dielectric layer and metal gate configuration for improved electrostatic control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a wide bandgap HEMT structure is used to achieve high breakdown voltage and high electron mobility, then the transistor can operate at high frequencies and high voltages, but the on-state resistance becomes relatively high
Solution Approach 1:
The patent applies local quality by creating a two-dimensional electron gas specifically at the AlGaN/GaAs interface region, concentrating high electron mobility properties where needed for conduction while maintaining the wide bandgap properties in other regions for high breakdown voltage. The quantum well is formed locally at the interface rather than throughout the entire structure.
Solution Approach 2:
The patent uses composite materials by combining AlGaN and GaAs layers to form a heterostructure. This composite structure leverages the wide bandgap of AlGaN for high voltage withstand while utilizing the high electron mobility of the interface electron gas for low on-state resistance, effectively resolving the contradiction between these two properties.
2Ease of operation
If the gate protrudes onto lateral faces of semiconductor layers to improve electrostatic control, then the transistor can achieve better switching characteristics, but the manufacturing complexity increases
Solution Approach 1:
The patent extends the gate electrode from a planar configuration into the third dimension by having it protrude onto lateral faces of the semiconductor layers. This dimensional extension improves electrostatic control over the channel without requiring excessively large gate lengths, achieving better switching characteristics while managing the complexity through a well-defined three-dimensional structure.
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
The design achieves lower on-state resistivity and higher breakdown voltage, ensuring effective operation as a normally-off transistor with reduced electron mobility degradation and enhanced voltage withstand, suitable for high-power, high-frequency applications.
Implementation Method 1
A barrier layer 12 is formed on a channel layer 11, so as to form a two-dimensional electron gas 13 at the interface between the layers 11 and 12
Implementation Method 2
The layer 102 is formed on a charge-trapping layer 101
Data Source
AI summary
A normally-off heterojunction field-effect transistor is provided, including a superposition of a first layer, of III-N type, and of a second layer, of III-N type, so as to form a two-dimensional electron gas; a stack of an n-doped third layer making electrical contact with the second layer, and of a p-doped fourth layer placed in contact with and on the third layer, a first conductive electrode and a second conductive electrode making electrical contact with the two-dimensional electron gas; a dielectric layer disposed against a lateral face of the fourth layer; and a control electrode separated from the lateral face of the fourth layer by the dielectric layer.