Carbon-Graded AlGaN Buffer for Nitride Semiconductor Leakage
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Solution Overview
Problem
The challenge in producing high-quality nitride semiconductor devices lies in controlling leakage currents and residual carrier concentrations due to lattice mismatch and thermal expansion differences between Si substrates and nitride semiconductors, which affects breakdown voltage and crystallinity.
Innovation Solution
A compound semiconductor device with a multilayer structure featuring a first AlN buffer layer and a second AlGaN buffer layer with increasing carbon concentration from the lower surface to the upper surface, optimized through specific growth conditions to reduce residual carrier concentrations and inhibit off-leakage currents while maintaining crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a buffer layer is formed with relatively large thickness to resolve lattice mismatch and thermal expansion difference between Si and nitride semiconductor, then the quality of nitride semiconductor layer is improved, but off-leakage current increases due to residual carrier concentration in the buffer layer
Solution Approach 1:
The patent applies local quality by creating a carbon concentration gradient within the buffer layer, where the carbon concentration varies from the lower surface to the upper surface. This gradient structure provides different local properties: the lower portion with lower carbon concentration maintains good crystallinity for lattice matching, while the upper portion with higher carbon concentration suppresses residual carrier generation, thereby reducing off-leakage current.
Solution Approach 2:
The patent changes the chemical composition parameter by introducing carbon into the buffer layer and controlling its concentration distribution. The carbon concentration is specifically designed to increase from the lower surface toward the upper surface of the buffer layer, which modifies the electrical properties to suppress residual carriers while maintaining structural integrity for lattice mismatch compensation.
2Reliability
If carbon is added to the buffer layer to suppress residual carrier concentration, then off-leakage current is reduced, but crystallinity may deteriorate
Solution Approach 1:
The patent uses local quality by spatially distributing carbon concentration non-uniformly in the buffer layer. The lower surface region has lower carbon concentration to preserve crystallinity and lattice matching quality, while the upper region has higher carbon concentration to suppress residual carriers. This localized differentiation resolves the contradiction between crystallinity and off-leakage current suppression.
Solution Approach 2:
The patent applies preliminary action by pre-designing the carbon concentration gradient before device operation. The carbon distribution is optimized in advance during manufacturing, with the concentration profile predetermined to achieve both good crystallinity at the growth interface and effective carrier suppression in the bulk buffer region, preventing off-leakage current before it occurs.
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 approach effectively reduces off-leakage currents and enhances breakdown voltage while ensuring high crystallinity of the semiconductor multilayer structure, thereby improving the reliability of nitride semiconductor devices.
Implementation Method 1
the second buffer layer contains carbon, and the concentration of carbon in the second buffer layer increases with increasing distance from a lower surface of the second buffer layer toward an upper surface of the second buffer layer
Data Source
AI summary
A compound semiconductor device includes: a compound semiconductor multilayer structure including a first buffer layer composed of AlN; and a second buffer layer composed of AlGaN and formed above the first buffer layer, wherein the second buffer layer contains carbon, and wherein the concentration of carbon in the second buffer layer increases with increasing distance from a lower surface of the second buffer layer toward an upper surface of the second buffer layer.