Dual-Gate GaN HEMT Threshold Voltage Control

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Solution Overview

Problem

Current high electron mobility transistors (HEMTs), particularly gallium nitride (GaN) HEMTs, require performance enhancement for improved high-frequency operations in applications like cell phones and radar equipment, as they face limitations in threshold voltage control and efficiency.

Innovation Solution

A semiconductor device with a gate stack structure similar to that of a flash memory is used, featuring a first and second gate with dielectric layers, where the second gate is electrically coupled to the source, enhancing the threshold voltage of the HEMT by fine-tuning the coupling ratio to achieve an enhancement-mode operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional single-gate HEMT structure is used, then device simplicity is maintained, but threshold voltage control is insufficient

Engineering Contradiction:

Improvethreshold voltage controlVSAvoidgate structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The gate structure is segmented into two separate gates (first gate and second gate) with different functions. The first gate controls the threshold voltage through dielectric layer coupling, while the second gate provides additional control capability. This segmentation allows independent optimization of threshold voltage control without overwhelming complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first gate is disposed within the structure formed by the second gate, creating a nested configuration where the first gate is positioned between the second gate and the III-V compound layers. This nested arrangement enables compact integration of dual-gate functionality while maintaining precise threshold voltage control through the dielectric layers.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Loss of energy

If enhancement-mode operation is achieved through threshold voltage enhancement, then leakage is reduced, but device complexity increases

Engineering Contradiction:

Improveleakage reductionVSAvoidgate stack structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

Dielectric layers are introduced as intermediary elements between the gates and the III-V compound layers, and between the first and second gates. These dielectric layers enable electrical coupling and threshold voltage enhancement without direct contact, reducing leakage currents while maintaining a relatively simple gate stack structure that can be integrated into existing HEMT fabrication processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If high-frequency performance is improved through better threshold voltage control, then device efficiency increases, but manufacturing complexity increases

Engineering Contradiction:

Improvedevice efficiencyVSAvoidfabrication complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The dual-gate structure with dielectric layers serves multiple functions simultaneously: threshold voltage control, leakage reduction, and high-frequency performance enhancement. This multi-functionality is achieved through a gate stack configuration that can be integrated into existing HEMT fabrication processes, avoiding the need for entirely new manufacturing methodologies and maintaining reasonable ease of manufacture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 allows for improved threshold voltage control, enabling the HEMT to operate effectively in enhancement mode, enhancing high-frequency performance and reducing leakage, thus addressing the limitations of existing HEMTs.

Implementation Method 1

The second gate is disposed on the first gate and electrically insulated from the first gate

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Implementation Method 2

the second gate is electrically coupled to the source

Methodology Applied

Scientific EffectElectrical coupling: Conduction (electrical)

Implementation Method 3

a junction formed by two materials with different band gaps as carrier channels

Methodology Applied

Scientific EffectBand gap difference:

Implementation Method 4

gallium nitride (GaN) HEMTs have excellent high frequency performance

Methodology Applied

Scientific EffectHigh electron mobility:

Data Source

PatentUS11342439B2III-V field effect transistor and semiconductor structure

Publication Date: 2022.05.24 NUVOTON

AI summary

A semiconductor device and a semiconductor structure are disclosed. The semiconductor device includes a substrate, a first III-V compound layer, a second III-V compound layer, a source, a drain and a gate stack structure. The first III-V compound layer is disposed on the substrate. The second III-V compound layer is disposed on the first III-V compound layer. The source and the drain are disposed on opposite sidewall boundaries of the second III-V compound layer. The gate stack structure is disposed on the second III-V compound layer. The gate stack structure includes a first gate and a second gate. The first gate is disposed on the second III-V compound layer. The second gate is disposed on and electrically isolated from the first gate. The second gate is electrically coupled to the source.