HEMT with Segmented Gate Electrodes for Normally-Off Operation
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Solution Overview
Problem
Current silicon-based power devices face limitations in efficiency due to silicon's physical properties, leading to challenges in achieving high electron mobility and normally-off characteristics, which are addressed by developing high electron mobility transistors (HEMTs) using group III-V compound semiconductors with heterojunction structures.
Innovation Solution
A high electron mobility transistor design featuring a channel layer and channel supply layer generating a 2-dimensional electron gas, with multiple gate electrodes and resistive layers to induce a second gate voltage, enhancing the threshold voltage and achieving a normally-off characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gate electrode is used in conventional HEMT design, then the device structure is simple, but the threshold voltage control and normally-off characteristic are insufficient
Solution Approach 1:
The gate electrode is divided into multiple segments (first gate electrode and second gate electrode) positioned at different locations above the channel. This segmentation allows independent control of threshold voltage and normally-off characteristics, resolving the contradiction by enabling sophisticated electrical control without requiring a completely new device architecture.
Solution Approach 2:
A resistive layer is introduced as an intermediary element between the second gate electrode and the channel. This resistive layer mediates the electrical interaction, allowing the second gate electrode to influence the threshold voltage through controlled resistance, thereby achieving normally-off characteristics without direct contact or complex structural modifications.
2Productivity
If silicon-based materials are used in power devices, then the manufacturing process isๆ็, but the electron mobility and conversion efficiency are limited
Solution Approach 1:
The patent employs compound semiconductor materials (such as GaN) forming heterojunction structures with different bandgaps. This composite material approach enables high electron mobility and high conversion efficiency by utilizing the unique properties of compound semiconductors, while the heterojunction design allows for controlled carrier transport and threshold voltage adjustment.
3Loss of energy
If the gate voltage is 0 V in conventional HEMT, then the device is in normally-on state with low resistance, but current and power loss occur continuously
Solution Approach 1:
The second gate electrode, through the resistive layer, creates a preliminary opposing electric field that counteracts the natural channel formation. This preliminary anti-action prevents spontaneous current flow at 0 V gate voltage, achieving normally-off characteristics and eliminating continuous power loss without requiring complex biasing circuits.
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 increases the threshold voltage and improves the normally-off characteristic of HEMTs, reducing power loss and enhancing the efficiency of power conversion systems by effectively controlling current flow between the drain and source electrodes.
Implementation Method 1
a semiconductor layer having relatively large polarizability may induce a 2-dimensional electron gas (2DEG) in the other semiconductor layer bonded to the semiconductor layer. Here, the 2DEG may have very high electron mobility.
Implementation Method 2
the first gate electrode may be configured to induce a second gate voltage into the floating electrode if a first gate voltage is applied to the first gate electrode.
Data Source
AI summary
According to example embodiments, a high electron mobility transistor includes: a channel layer including a first semiconductor material; a channel supply layer on the channel layer and configured to generate a 2-dimensional electron gas (2DEG) in the channel layer, the channel supply layer including a second semiconductor material; source and drain electrodes spaced apart from each other on the channel layer, and an upper surface of the channel supply layer defining a gate electrode receiving part; a first gate electrode; and at least one second gate electrode spaced apart from the first gate electrode and in the gate electrode receiving part. The first gate electrode may be in the gate electrode receiving part and between the source electrode and the drain electrode. The at least one second gate electrode may be between the source electrode and the first gate electrode.