GaN Epitaxial Substrate With Mn Gradient for 2DEG Protection
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Solution Overview
Problem
Current GaN epitaxial substrates used in GaN-HEMTs face challenges in preventing Mn diffusion to the 2DEG region, leading to reduced electron mobility and increased manufacturing costs, with existing methods either requiring thick undoped buffer layers or low Mn doping concentrations, which are difficult to maintain and result in current collapse phenomena.
Innovation Solution
A GaN epitaxial substrate with a steep Mn concentration gradient in the [0001] axis direction and a C-containing layer in the GaN buffer layer, inhibiting Mn diffusion by controlling the Mn concentration distribution, allowing for a thinner buffer layer and maintaining semi-insulating properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick undoped GaN buffer layer is provided to prevent Mn diffusion, then Mn diffusion to the 2DEG region is reduced, but the degree of freedom in design is impaired and manufacturing cost increases
Solution Approach 1:
The patent applies local quality by creating a specific Mn concentration distribution profile within the GaN buffer layer, where the Mn concentration varies spatially to achieve high Mn concentration near the substrate interface for semi-insulating properties and low Mn concentration near the 2DEG region to prevent diffusion. This localized variation in Mn concentration allows the buffer layer to simultaneously maintain semi-insulating properties and prevent Mn diffusion without requiring excessive thickness.
Solution Approach 2:
The patent changes the Mn concentration parameter within the GaN buffer layer to resolve the contradiction. By controlling the Mn concentration to be 1×10^17 atoms/cm³ or more at a first position and 1×10^15 atoms/cm³ or less at a second position, the patent achieves both semi-insulating properties and prevention of Mn diffusion to the 2DEG region, eliminating the need for a thick undoped buffer layer.
2Reliability
If a steep Mn concentration gradient is created to prevent diffusion, then Mn diffusion to the 2DEG region is prevented, but a thinner buffer layer is required which may affect device performance
Solution Approach 1:
The patent changes the Mn concentration parameter to create a steep gradient that prevents Mn diffusion while allowing for a thinner buffer layer. By establishing specific Mn concentration thresholds (1×10^17 atoms/cm³ at the first position and 1×10^15 atoms/cm³ at the second position), the patent achieves effective diffusion prevention without requiring excessive buffer layer thickness, thus maintaining design flexibility.
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 solution effectively prevents Mn diffusion to the 2DEG region, enhancing the GaN-HEMT's performance and design flexibility while reducing manufacturing costs by maintaining semi-insulating properties and minimizing current collapse.
Implementation Method 1
The transition metal element and the Group 12 element act as acceptors, and therefore, there is an effect of reducing a concentration of a carrier in the GaN substrate by compensating for a background donor unintentionally introduced into the GaN substrate.
Implementation Method 2
The diffusion of Mn is caused by thermal diffusion, and therefore, the Mn concentration decreases as a diffusion distance is increased.
Implementation Method 3
a GaN buffer layer epitaxially grown on the GaN substrate
Data Source
AI summary
A GaN epitaxial substrate contains a GaN substrate and a GaN buffer layer epitaxially grown on the GaN substrate. The GaN epitaxial substrate includes a point A and a point B positioned on a straight line parallel to a [0001] axis passing through the point A, the point B being present in a [0001] axis direction relative to the point A. The point A is present in the GaN substrate or the GaN buffer layer, the point B is present in the GaN buffer layer, a ratio ([Mn]B/[Mn]A) is 1/100, and a distance between the point A and the point B is 0.7 μm or less.