AlGaN Multilayer Grading for Leakage Current Reduction
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Solution Overview
Problem
The challenge in fabricating high-power nitride semiconductor devices is the increase in leakage current due to defective GaN layers, which affects the breakdown voltage and overall device performance, particularly in heterojunction Field Effect Transistors (HFETs).
Innovation Solution
A semiconductor device structure incorporating an AlGaN multilayer with varying aluminum composition along the depositing direction and a SixNy layer is introduced, which reduces vertical and surface leakage currents, thereby enhancing the breakdown voltage and maintaining the two-dimensional electron gas (2DEG) characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a GaN buffer layer is used to reduce leakage current, then leakage current is reduced, but strain and quality of the epitaxial layer are directly affected
Solution Approach 1:
The AlGaN layer is divided into multiple sub-layers with different aluminum compositions (first AlGaN layer with 10-30% Al, second AlGaN layer with 30-50% Al). This segmentation allows each sub-layer to perform specific functions: the first layer reduces leakage current while the second layer manages strain, thereby resolving the contradiction between leakage reduction and epitaxial layer quality
Solution Approach 2:
Different regions of the AlGaN barrier layer have different aluminum compositions tailored to specific local requirements. The lower Al composition region (10-30%) is optimized for leakage current reduction, while the upper Al composition region (30-50%) is optimized for strain management and epitaxial layer quality, allowing simultaneous achievement of both goals
2Object-generated harmful factors
If Al composition is increased to reduce leakage current, then leakage current is reduced, but breakdown voltage decreases
Solution Approach 1:
The AlGaN barrier layer is designed with spatially varying aluminum composition: a first AlGaN layer with lower Al content (10-30%) near the GaN channel to maintain high breakdown voltage, and a second AlGaN layer with higher Al content (30-50%) above it to reduce leakage current. This local quality differentiation resolves the contradiction between leakage reduction and breakdown voltage maintenance
Solution Approach 2:
The barrier layer is segmented into multiple AlGaN layers with graded aluminum compositions. This segmentation creates a composition gradient that simultaneously achieves leakage current reduction (through the higher Al content layer) and breakdown voltage maintenance (through the lower Al content layer), eliminating the need to choose one parameter over the other
Data Source
AI summary
A nitride semiconductor power device includes an AlGaN multilayer, which has changeable Al composition along a depositing direction, and SixNy layer, so as to minimize an increase in a leakage current and a decrease in a breakdown voltage, which are caused while fabricating a heterojunction type HFET device. A semiconductor device includes a buffer layer, an AlGaN multilayer formed on the buffer layer, a GaN channel layer formed on the AlGaN multilayer, and an AlGaN barrier layer formed on the AlGaN multilayer, wherein aluminum (Al) composition of the AlGaN multilayer changes along a direction that the AlGaN multilayer is deposited.