GaN Rectifier Integration with HEMTs via Segmented Heterostructure
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Solution Overview
Problem
Existing rectifiers based on SBD or p-i-n diodes are not compatible with HEMT structures, leading to performance loss, and AlGaN/GaN heterojunctions with metal-AlGaN Schottky barriers result in higher turn-on voltages and on-resistances, which are undesirable in high-voltage power electronics.
Innovation Solution
A rectifier structure is developed using a gate-last approach with a buffer layer and III-V compound layers grown using MOVPE, featuring a negatively charged region and a gate dielectric to reduce leakage current and modulate threshold voltage, allowing for integration with HEMTs while maintaining low forward turn-on voltages and high reverse breakdown voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SBD or p-i-n diode rectifiers are used, then high reverse breakdown voltage is achieved, but compatibility with HEMT structures is lost and performance deteriorates
Solution Approach 1:
The patent merges the rectifier and HEMT structures into a single integrated device, combining the high reverse breakdown voltage capability of SBD/p-i-n diodes with the high electron mobility of HEMTs. The rectifier region and HEMT region share the same AlGaN/GaN heterostructure substrate, enabling both functions to coexist without performance loss.
Solution Approach 2:
The AlGaN/GaN heterostructure serves multiple functions: it provides the high reverse breakdown voltage characteristic of rectifiers while simultaneously providing the high electron mobility channel required for HEMT operation. This universal material system enables both rectification and high-frequency switching functions in a single device.
2Ease of manufacture
If metal-AlGaN Schottky barrier is used, then rectifier structure is formed, but turn-on voltage and on-resistance increase
Solution Approach 1:
The patent applies different local structures to different regions: the rectifier region uses a metal-AlGaN Schottky barrier for easy fabrication, while the HEMT region uses a modified heterostructure with reduced aluminum content and optimized thickness to achieve low turn-on voltage. This local differentiation allows each region to optimize its own performance characteristics.
Solution Approach 2:
The patent changes key parameters in the HEMT region compared to the rectifier region: the AlGaN barrier layer thickness is reduced, the aluminum composition is lowered, and the GaN channel thickness is optimized. These parameter changes reduce the turn-on voltage and on-resistance while maintaining the rectifier's high breakdown voltage capability.
3Device complexity
If rectifier integration with HEMTs is attempted using conventional structures, then device complexity is reduced, but performance loss occurs
Solution Approach 1:
The integrated device is segmented into distinct functional regions: a rectifier region with metal-AlGaN Schottky contact for high breakdown voltage, and a HEMT region with optimized heterostructure for low turn-on voltage and high electron mobility. This segmentation allows each region to be independently optimized while maintaining overall device performance.
Solution Approach 2:
The AlGaN/GaN heterostructure serves as an intermediary between the metal contact and the semiconductor channel, providing a graded transition that manages the trade-off between Schottky barrier height and carrier mobility. This intermediate layer enables smooth carrier transport while maintaining the rectifying characteristic.
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 solution enables the integration of rectifiers with HEMTs, achieving low on-state resistance and short reverse recovery time, thus improving power conversion efficiency and reducing circuit complexity and cost.
Implementation Method 1
a buffer layer and III-V compound layers grown using MOVPE
Implementation Method 2
A HEMT is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel
Implementation Method 3
featuring a negatively charged region and a gate dielectric to reduce leakage current and modulate threshold voltage
Data Source
AI summary
An integrated circuit device includes a first III-V compound layer, a second III-V compound layer over the first III-V compound layer, a gate dielectric over the second III-V compound layer, and a gate electrode over the gate dielectric. An anode electrode and a cathode electrode are formed on opposite sides of the gate electrode. The anode electrode is electrically connected to the gate electrode. The anode electrode, the cathode electrode, and the gate electrode form portions of a rectifier.