III-Nitride Epitaxial Structure With Intermediate Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing epitaxial structures in RF devices, such as those with GaN channel and AlGaN barrier layers, suffer from limited carrier limitation capability, leading to lower two-dimensional electron gas (2DEG) concentration and poor electron mobility due to interface roughness and indium addition in the barrier layer.
Innovation Solution
An epitaxial structure with an intermediate layer having a specific aluminum content variation between the channel and barrier layers, where the aluminum content in the intermediate layer is greater than in the barrier layer, and varies linearly or stepwise along the growth direction to improve carrier limitation capability and interface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If indium is added in the barrier layer to increase carrier limitation capability, then 2DEG concentration is improved, but interface roughness increases and electron mobility deteriorates
Solution Approach 1:
The barrier layer is segmented into multiple sub-layers with different indium contents. The first barrier layer has higher indium content (0.1-0.5) for strong carrier limitation, while the second barrier layer has lower indium content (0.05-0.3) for smoother interface, resolving the contradiction between carrier limitation capability and interface quality
Solution Approach 2:
Different regions of the barrier layer have different indium compositions optimized for their specific functions. The first barrier layer near the channel uses higher indium for maximum carrier limitation, while the second barrier layer uses lower indium to reduce interface roughness effects on electron mobility
2Quantity of substance
If indium is added in the barrier layer to improve carrier limitation capability, then 2DEG concentration is improved, but electron mobility deteriorates
Solution Approach 1:
The barrier layer is divided into two sub-layers with different indium compositions. The first barrier layer (higher In: 0.1-0.5) provides strong carrier limitation for high 2DEG concentration, while the second barrier layer (lower In: 0.05-0.3) reduces interface roughness to maintain high electron mobility
Solution Approach 2:
The barrier structure uses a composite of two AlGaN layers with different indium compositions, combining the high carrier limitation capability of high-In AlGaN with the low interface roughness characteristics of low-In AlGaN to achieve both high 2DEG concentration and high electron mobility
3Manufacturing precision
If aluminum content in the intermediate layer is increased to improve interface quality, then surface roughness is reduced, but lattice mismatch may increase
Solution Approach 1:
The aluminum content in the intermediate layer is precisely controlled within the range of 0.05-0.2, which is sufficient to reduce surface roughness and improve interface quality while maintaining lattice constant stability and avoiding excessive lattice mismatch
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 configuration enhances electron mobility, improves 2DEG characteristics, and reduces surface roughness, thereby enhancing the operating characteristics of the device.
Implementation Method 1
semiconductor epitaxy has the advantages of high purity, good thickness control, etc.
Implementation Method 2
the two-dimensional electron gas (2DEG) produced by the polarization effect
Data Source
AI summary
An epitaxial structure includes a substrate, a buffer layer, a channel layer, an intermediate layer, and a barrier layer. The buffer layer is disposed on the substrate, the channel layer is disposed on the buffer layer, the barrier layer is disposed on the channel layer, and the intermediate layer is disposed between the channel layer and the barrier layer. The chemical composition of the barrier layer is Alx1Iny1Gaz1N, and the chemical composition of the intermediate layer is Alx2Iny2Gaz2N. The lattice constant of the barrier layer is greater than the lattice constant of the intermediate layer. The aluminum (Al) content of at least a portion of the intermediate layer is greater than the Al content of the barrier layer.