GaN MOSFET Gate Structure for Threshold Voltage Control
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Solution Overview
Problem
MOS type field effect transistors (MOSFETs) using nitride semiconductors face challenges in controlling the threshold voltage, which is essential for their performance in power conversion devices.
Innovation Solution
The semiconductor device incorporates a specific structure with a GaN-based semiconductor layer, a first gate electrode, and a dielectric structure body that includes an intermediate conductor layer and dielectric layers with polarized charges at their interfaces, generating a potential to improve and control the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a MOS type field effect transistor (MOSFET) using nitride semiconductor is constructed to achieve high breakdown voltage and high speed responsiveness, then the transistor becomes suitable for power conversion devices, but the threshold voltage becomes difficult to control to an arbitrary value
Solution Approach 1:
The gate structure is segmented into multiple functional layers: a gate electrode, an insulating layer, and a nitride semiconductor layer. Additionally, a specific structure body is introduced between the gate electrode and nitride semiconductor layer, comprising an intermediate layer and dielectric layers with interfaces. This segmentation allows independent optimization of each layer's properties to achieve both high breakdown voltage and controllable threshold voltage.
Solution Approach 2:
Different regions of the gate structure are assigned different material properties and functions. The insulating layer provides electrical isolation, the intermediate layer suppresses charge generation at specific interfaces, and the dielectric layers create controlled potential differences. This local differentiation of material qualities enables precise control of threshold voltage while maintaining high breakdown characteristics.
2Productivity
If a conventional MOSFET structure with metal-oxide-semiconductor gate is used to achieve high speed switching, then energy conversion efficiency is improved, but charge generation at interfaces and electron-hole leakage occur
Solution Approach 1:
An intermediate layer is introduced as a mediator between the insulating layer and the nitride semiconductor layer. This intermediate layer specifically suppresses charge generation at the interfaces where charge accumulation would normally occur. By placing this intermediary layer at the critical interface region, harmful charge generation is prevented while maintaining the high-speed switching performance of the MOSFET structure.
3Productivity
If the nitride semiconductor layer is used to achieve high electron mobility and high energy conversion efficiency, then the transistor performance is improved, but the threshold voltage control becomes difficult
Solution Approach 1:
A structure body comprising dielectric layers with interfaces is constructed preliminarily between the gate electrode and nitride semiconductor layer. These dielectric layers are designed to generate specific potential differences at their interfaces before the transistor operates. This preliminary structural arrangement pre-establishes the electrical conditions needed to control threshold voltage, allowing the nitride semiconductor to maintain its high electron mobility while the threshold voltage becomes controllable through the pre-configured potential landscape.
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 configuration enhances the controllability of the threshold voltage, improving the performance and energy conversion efficiency of the MOSFETs by suppressing charge generation at interfaces and preventing electron and hole leakage.
Implementation Method 1
a first insulating layer, a first structure body, and a first gate electrode are laminated on a semiconductor layer in this order. The first structure body includes an intermediate layer, a first layer, and a second layer. The first layer and the second layer which each have dielectric property
Implementation Method 2
a first layer having dielectric property between the first gate electrode and the first intermediate layer, and a second layer having dielectric property between the first gate electrode and the first layer
Implementation Method 3
The first structure body has a first intermediate layer made of a conductor to suppress generation of charges at respective interfaces with adjacent layers
Implementation Method 4
since the nitride semiconductor has a high electron mobility, the transistor can electrically perform a high speed response
Implementation Method 5
high withstand characteristics are obtained, due to electrical material characteristics of the nitride semiconductor that is a material with a wide band gap
Data Source
AI summary
In one embodiment, a semiconductor device is provided with a semiconductor layer made of a nitride semiconductor, a first gate electrode, a first structure body between the first gate electrode and the semiconductor layer, and a first insulating layer between the semiconductor layer and the first structure body. The first structure body has a first intermediate layer made of a conductor to suppress generation of charges at respective interfaces with adjacent layers, a first layer having dielectric property between the first gate electrode and the first intermediate layer, and a second layer having dielectric property between the first gate electrode and the first layer, and has dipoles at an interface between the first layer and the second layer.