Composite Buffer Layer Carbon Grading for GaN Breakdown Control
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Solution Overview
Problem
GaN HEMTs face premature breakdown due to uneven carbon concentration in the buffer layer, leading to excessive leakage, as traditional doping methods result in inconsistent carbon distribution across the wafer, affecting device performance and breakdown voltage.
Innovation Solution
A semiconductor structure with a composite buffer layer comprising stacked sub-buffer layers with varying carbon concentrations, where the carbon concentration is higher at the center and lower at the edge, or vice versa, to ensure uniformity and prevent excessive leakage, and a preparation method to achieve this structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional doping method is used to dope carbon element in buffer layer, then carbon element can be introduced to improve resistance, but carbon concentration becomes uneven between center and edge of wafer
Solution Approach 1:
The buffer layer is divided into multiple sub-buffer layers (first sub-buffer layer, second sub-buffer layer, third sub-buffer layer) with different carbon doping concentrations. Each sub-buffer layer has a specific carbon concentration range, creating a graded structure that prevents excessive carbon accumulation at center or edge while maintaining overall buffer layer resistance.
Solution Approach 2:
Different regions of the buffer layer are assigned different carbon doping concentrations. The first sub-buffer layer has higher carbon concentration (1×10^18 to 1×10^19 atoms/cm³), the second sub-buffer layer has intermediate concentration (5×10^17 to 5×10^18 atoms/cm³), and the third sub-buffer layer has lower concentration (1×10^17 to 1×10^18 atoms/cm³). This local variation in carbon concentration optimizes both resistance and uniformity.
2Reliability
If carbon concentration is increased to reduce leakage, then resistivity improves, but breakdown voltage decreases due to excessive carbon at center or edge
Solution Approach 1:
The carbon doping concentration parameter is varied across different sub-buffer layers. By changing the carbon concentration from high in the first sub-buffer layer to low in the third sub-buffer layer, the structure achieves optimal leakage resistance without excessive carbon accumulation that would cause premature breakdown.
Solution Approach 2:
The buffer layer is constructed as a composite structure with multiple sub-buffer layers, each having different carbon doping concentrations. This composite approach allows the buffer layer to simultaneously achieve high resistivity for leakage prevention and appropriate breakdown voltage by distributing carbon concentration optimally across the structure.
Data Source
AI summary
Disclosed are a semiconductor structure and a preparation method thereof. The semiconductor structure includes a substrate, including a first region arranged at the center of the substrate and a second region arranged at the periphery of the first region; and a composite buffer layer arranged on the substrate, including a carbon-containing first buffer layer including at least one set of a first sub-buffer layer and a second sub-buffer layer stacked in layers; therein, a carbon concentration of the first sub-buffer layer arranged at the first region is higher than that arranged at the second region; and a carbon concentration of the second sub-buffer layer arranged at the first region is lower than that at arranged the second region. Therefore, uniformity of the carbon concentration of the composite buffer layer is improved to improve resistivity of the composite buffer layer, so as to increase breakdown voltage and improve device performance.