HEMT Barrier Layer Doping for High Breakdown Voltage
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face limitations in breakdown voltage and reliability due to lattice and thermal mismatches between substrates and epitaxial layers, leading to reduced voltage applications and increased parasitic capacitance.
Innovation Solution
The HEMT design incorporates a barrier layer with doped semiconductor regions extending from the top to the bottom surface, positioned between the drain and gate conductor, which reduces drain electric field intensity and enhances breakdown voltage, stability, and eliminates the need for thick epitaxial layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of an epitaxial layer on a substrate is increased to reduce the impact of drain electric field and achieve higher breakdown voltage, then breakdown voltage is improved, but lattice mismatch and thermal mismatch between the substrate and the epitaxial layer make it difficult to increase the thickness on large-size substrates
Solution Approach 1:
The patent divides the barrier layer into multiple segments: an undoped barrier layer and a doped barrier layer with different doping concentrations. This segmentation allows each layer to serve specific functions - the undoped layer provides high electron mobility while the doped layer reduces electric field intensity at the drain, achieving high breakdown voltage without requiring excessive total thickness that would cause lattice mismatch issues
Solution Approach 2:
The patent applies local quality by creating a doped barrier layer with specific doping concentrations in certain regions (particularly near the drain) while keeping other regions undoped. This localized doping optimizes the electric field distribution specifically where needed (at the drain edge) without compromising the overall electron mobility in the channel region, thereby achieving high breakdown voltage with controlled layer thickness
2Strength
If a drain field plate is introduced to reduce the impact of drain electric field, then breakdown voltage is improved, but parasitic capacitance (drain-gate capacitance Cgd and drain-source capacitance Cds) is notably increased, reducing transforming efficiency and reliability
Solution Approach 1:
The patent extracts the electric field management function from the traditional drain field plate structure and relocates it into the barrier layer itself through doping. By creating a doped barrier layer with appropriate doping concentrations, the patent achieves electric field reduction at the drain without requiring an additional field plate structure, thereby eliminating the parasitic capacitance issues associated with field plates while maintaining high breakdown voltage
Solution Approach 2:
The doped barrier layer acts as an intermediary structure between the channel layer and the drain. Instead of using a field plate that would create parasitic capacitance, the patent uses the doped barrier layer as a mediator to manage the electric field distribution. The doping in the barrier layer provides the necessary electric field control function while avoiding the capacitance problems of traditional field plate designs
3Strength
If a multi-layer field plate structure is introduced to reduce the impact of drain electric field, then breakdown voltage is improved, but device complexity is increased
Solution Approach 1:
The patent merges the barrier layer and the electric field management function into a single integrated structure. Instead of adding a separate multi-layer field plate structure on top of the barrier layer, the patent combines the barrier function and electric field control function within the barrier layer itself through strategic doping. This integration simplifies the device structure while achieving the same breakdown voltage improvement that would otherwise require complex field plate arrangements
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 design achieves a high breakdown voltage exceeding 900 V, improving the reliability and stability of HEMTs while reducing process complexity and parasitic capacitance.
Implementation Method 1
The barrier layer comprises a doped semiconductor region extending from a top surface to a bottom surface of the barrier layer and located between the drain and the gate conductor
Data Source
AI summary
The HEMT includes a channel layer, a barrier layer, a drain, and a gate conductor. The barrier layer is disposed on the channel layer. The drain is disposed on the barrier layer. The gate conductor is disposed on the barrier layer. The barrier layer comprises a doped semiconductor region extending from a top surface to a bottom surface of the barrier layer and located between the drain and the gate conductor.