Nitride Semiconductor Multi-Layer Substrate With Lateral Conductivity
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Solution Overview
Problem
Existing semiconductor multi-layer substrates face challenges in reducing the total thickness of nitride semiconductor layers while maintaining necessary withstand voltage, leading to increased production costs and leakage currents due to the inefficiencies in buffer layer configurations.
Innovation Solution
A semiconductor multi-layer substrate is designed with a buffer layer, an electric-field control layer, and an electric-field relaxation layer, where the electric-field control layer has conductivity in the substrate's lateral direction, and the resistance ratio between the electric-field relaxation layer and the buffer layer is controlled to optimize the electric field distribution, reducing the total thickness while maintaining adequate withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer with repeated AlN and GaN layers is used to alleviate thermal expansion and lattice constant differences, then the epitaxial growth of nitride semiconductor on different substrate is improved, but the leakage current increases and the total thickness of nitride semiconductor layers must be increased to maintain withstand voltage
Solution Approach 1:
The patent changes the material composition parameter by introducing AlGaN layers with varying aluminum compositions into the buffer layer structure. This allows optimization of the buffer layer's electrical properties to reduce leakage current while maintaining its mechanical function of accommodating thermal and lattice mismatches between the substrate and nitride semiconductor layers.
Solution Approach 2:
The patent employs a composite buffer layer structure combining AlN, GaN, and AlGaN layers. This composite structure leverages the advantages of each material: AlN for thermal and lattice mismatch accommodation, GaN for low leakage current, and AlGaN for tunable electrical properties, thereby resolving the contradiction between growth quality and leakage current reduction.
2Reliability
If the total thickness of nitride semiconductor layers is increased to ensure withstand voltage, then the reliability is improved, but the production cost increases and throughput decreases
Solution Approach 1:
The patent optimizes the electrical field distribution by controlling the thickness and composition parameters of buffer layer components. This allows achieving the required withstand voltage with a reduced total thickness of nitride semiconductor layers, thereby decreasing crystal growth time and increasing production throughput while maintaining reliability.
Solution Approach 2:
The patent replaces the reliance on increased physical thickness (mechanical approach) with an optimized electrical field distribution through compositional engineering. By carefully designing the buffer layer's electrical properties, the patent achieves high withstand voltage with thinner active layers, reducing production time and cost.
3Reliability
If a buffer layer with GaN and AlN layers is used, then the thermal expansion and lattice constant differences are alleviated, but a two-dimensional electron gas is produced at the AlN-GaN interface causing lateral leakage
Solution Approach 1:
The patent applies local quality by creating regions with different aluminum compositions within the buffer layer. The AlGaN layers have locally optimized composition to control electron concentration and prevent two-dimensional electron gas formation at interfaces, thereby eliminating lateral leakage while maintaining lattice matching benefits.
Solution Approach 2:
The patent changes the compositional parameter by introducing aluminum gradient layers (AlGaN) with varying aluminum content. This gradual composition change prevents abrupt interface formation that would generate two-dimensional electron gas, thereby reducing lateral leakage current while preserving the buffer layer's lattice-matching function.
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 solution effectively reduces the total thickness of nitride semiconductor layers relative to the necessary withstand voltage, thereby decreasing production costs and minimizing leakage currents, while optimizing the electric field distribution for improved semiconductor performance.
Implementation Method 1
an electric-field control layer which is formed on the buffer layer and made of a nitride semiconductor, and has conductivity in a substrate lateral direction
Implementation Method 2
a ratio of an electric field share between the electric-field relaxation layer and the buffer layer is controlled by a ratio between a thickness of the electric-field relaxation layer and a thickness of the buffer layer
Data Source
AI summary
A semiconductor multi-layer substrate includes a substrate, a buffer layer formed on the substrate and made of a nitride semiconductor, an electric-field control layer formed on the buffer layer and made of a nitride semiconductor, the electric-field control layer having conductivity in the substrate's lateral direction, an electric-field relaxation layer formed on the electric-field control layer and made of a nitride semiconductor, and an active layer formed on the electric-field relaxation layer and made of an nitride semiconductor. A resistance in the substrate's lateral direction of the electric-field control layer is equal to or smaller than 10 times a resistance of the electric-field relaxation layer, and a ratio of an electric field share between the electric-field relaxation layer and the buffer layer is controlled by a ratio between a thickness of the electric-field relaxation layer and a thickness of the buffer layer.