GaN HEMT Threshold Voltage Control via Fluorine Doping
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Solution Overview
Problem
Conventional semiconductor devices, particularly HEMTs, face challenges in achieving high breakdown voltage and low on-resistance due to the limitations of silicon-based materials, and struggle to realize normally off operation due to the inherent normally on nature of HEMTs without a gate voltage.
Innovation Solution
The implementation of a GaN-based HEMT with a gate recess structure and a fluorine region containing high concentrations of fluorine, which reduces nitrogen vacancies and increases the threshold voltage, allowing for normally off operation and improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gate recess structure is applied to HEMT to increase threshold voltage and realize normally off operation, then the threshold voltage is improved, but the manufacturing complexity increases due to trench formation and additional processing steps
Solution Approach 1:
The patent applies preliminary action by forming the gate recess structure and fluorine region during the epitaxial growth process itself, rather than adding separate processing steps afterward. The recess is formed and fluorine is introduced concurrently with layer deposition, which simplifies the overall manufacturing process while still achieving the desired threshold voltage increase for normally off operation
Solution Approach 2:
The patent changes physical and chemical parameters by introducing fluorine atoms into specific regions of the nitride semiconductor layer. This chemical modification alters the local electrical properties and threshold voltage characteristics, enabling normally off operation without requiring complex structural modifications beyond the gate recess
2Reliability
If nitride semiconductor is used to improve breakdown voltage and reduce on-resistance beyond silicon limits, then the electrical performance is improved, but the difficulty of detecting and measuring increases due to material properties
Solution Approach 1:
The patent uses fluorine as an intermediary element that modifies the nitride semiconductor properties in a controlled manner. The fluorine atoms act as mediators to adjust the electrical characteristics and threshold voltage, making the device behavior more predictable and easier to characterize despite the inherent difficulties of measuring nitride semiconductor properties
3Ease of operation
If conventional HEMT structure is used without gate voltage application, then the device simplicity is maintained, but the normally off operation cannot be realized
Solution Approach 1:
The patent applies local quality by creating a fluorine-rich region specifically in and around the gate recess area. This localized chemical modification creates a strong electric field effect that enables threshold voltage control and normally off operation, while the rest of the device maintains its simple HEMT structure. The fluorine is concentrated where needed to provide gate control without complicating the overall device architecture
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 enables the realization of HEMTs with higher threshold voltages and reduced on-resistance, effectively addressing the limitations of silicon-based materials and achieving stable operation in power supply circuits and computers.
Implementation Method 1
a region containing fluorine, the region reducing nitrogen vacancies in a nitride semiconductor
Implementation Method 2
increase the threshold voltage of the HEMT by extinguishing the two dimensional electron gas
Data Source
AI summary
A semiconductor device according to an embodiment includes a first nitride semiconductor layer; a second nitride semiconductor layer located on the first nitride semiconductor layer, a first and second electrode located on or above the first nitride semiconductor layer; a trench located in the second nitride semiconductor layer between the first electrode and the second electrode, and including a bottom surface and a side surface, the bottom surface being located in one of the first nitride semiconductor layer and the second nitride semiconductor layer; a gate electrode located in the trench; a gate insulating layer located between the bottom surface and the gate electrode and between the side surface and the gate electrode; and a region located in at least one of the first nitride semiconductor layer and the second nitride semiconductor layer, including a first portion adjacent to the bottom surface, and containing fluorine.