Normally-off HEMT with Depletion-forming Layer
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Solution Overview
Problem
Current silicon-based power devices, such as MOSFETs and IGBTs, face limitations in efficiency due to their physical properties and manufacturing processes, prompting the need for alternative semiconductor materials like group III-V compound semiconductors for improved power conversion systems. Specifically, achieving a normally-off high electron mobility transistor (HEMT) with reduced power consumption and leakage current remains a challenge.
Innovation Solution
A normally-off HEMT design incorporating a depletion-forming layer with a strip shape, where the gate electrode is positioned above the depletion-forming layer, and a p-type nitride semiconductor material is used to create a depletion region, reducing electron density and minimizing leakage current by increasing the energy bandgap, thereby enabling a normally-off state without current flow between the drain and source electrodes at 0 V gate voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a HEMT is designed to be normally-on state with low resistance between drain and source, then current flow is enabled for power conversion, but power consumption occurs and leakage current increases
Solution Approach 1:
The patent changes the electrical state parameters of the HEMT by introducing a depletion-forming layer with specific doping concentration (1×10^18 to 1×10^20 atoms/cm³) and thickness (50-200 nm), which modifies the energy band structure to achieve normally-off state while maintaining low on-resistance through optimized layer composition
2Loss of energy
If a negative voltage is applied to the gate electrode to achieve normally-off state, then power consumption is reduced, but device complexity and control difficulty increase
Solution Approach 1:
The patent fundamentally changes the threshold voltage parameter by incorporating a depletion-forming layer that creates a built-in potential barrier, allowing the HEMT to operate in normally-off state at zero gate voltage without requiring continuous negative bias control
3Reliability
If etching is performed at both ends of the depletion-forming layer to optimize performance, then device performance is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent extracts the depletion-forming layer as a separate, independently formable component with specific dimensional parameters, allowing it to be created through selective epitaxial growth or deposition processes without requiring complex etching operations at both ends
Solution Approach 2:
The patent segments the HEMT structure into distinct functional layers including the depletion-forming layer, channel layer, and barrier layer, each with optimized thickness and doping parameters that can be independently controlled during fabrication
4Ease of manufacture
If silicon-based materials are used in power devices, then manufacturing processes are well-established, but efficiency is limited by physical properties of silicon
Solution Approach 1:
The patent employs composite material structure combining different semiconductor layers with complementary properties - the depletion-forming layer provides carrier depletion capability while the channel layer maintains high electron mobility, achieving superior efficiency compared to single-material silicon devices
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 proposed HEMT achieves a normally-off state with reduced power consumption and increased breakdown voltage, minimizing leakage current and turn-on resistance, while simplifying the fabrication process by eliminating the need for etching at both ends of the depletion-forming layer.
Implementation Method 1
a p-type nitride semiconductor material is used to create a depletion region, reducing electron density and minimizing leakage current by increasing the energy bandgap
Implementation Method 2
minimizing leakage current by increasing the energy bandgap
Implementation Method 3
a semiconductor layer having a relatively high polarization rate may induce a two-dimensional electron gas (2DEG) in another semiconductor layer attached thereto, and the 2DEG may have very high electron mobility
Implementation Method 4
When a gate voltage of a HEMT is 0 V, power consumption may occur in a normally-on state in which a current flows between drain and source electrodes thereof due to a low resistance therebetween
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A normally-off high electron mobility transistor (HEMT) includes: a channel layer (120) having a first nitride semiconductor, a channel supply layer (130) on the channel layer, a source electrode (161) and a drain electrode (162) at sides of the channel supply layer, a depletion-forming layer (140) on the channel supply layer, a gate insulating layer (150) on the depletion-forming layer, and a gate electrode (170) on the gate insulation layer. The channel supply layer includes a second nitride semiconductor and is configured to induce a two-dimensional electron gas (2DEG) in the channel layer. The depletion-forming layer has at least two thicknesses and is configured to form a depletion region in at least a partial region of the 2DEG. The gate electrode contacts the depletion-forming layer.