AlN Anti-Diffusion Layer for Epitaxial Substrate
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Solution Overview
Problem
In the fabrication of HEMT devices, the diffusion of elements from the cap layer to the barrier layer can lead to deteriorated device characteristics, such as current collapse and unsuccessful PN junction formation, due to the diffusion of Ga and Mg elements in InAlN/GaN structures.
Innovation Solution
An epitaxial substrate configuration is developed with a channel layer, a barrier layer, an anti-diffusion layer made of AlN, and a cap layer, where the AlN layer serves as an anti-diffusion layer to prevent element diffusion, ensuring excellent device characteristics and enabling the formation of a PN junction with reduced reverse leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cap layer is formed on the barrier layer to control energy levels and improve contact characteristics, then device contact characteristics are improved, but Ga and Mg elements diffuse from the cap layer to the barrier layer causing device characteristics to deteriorate
Solution Approach 1:
An AlN layer is introduced as an intermediary between the cap layer and the InAlN barrier layer. This intermediate layer acts as a diffusion barrier that prevents Ga and Mg elements from the cap layer from diffusing into the InAlN barrier layer, while still allowing the cap layer to perform its function of controlling energy levels and improving contact characteristics.
2Adaptability or versatility
If a cap layer is formed to establish a PN junction with the InAlN barrier layer, then a PN junction structure is achieved, but element diffusion prevents successful PN junction formation
Solution Approach 1:
The AlN intermediate layer serves as a diffusion barrier that enables successful PN junction formation by preventing element diffusion. This allows the cap layer to establish proper electrical junction characteristics with the InAlN barrier layer without contamination from diffusing Ga and Mg elements.
3Stability of the object's composition
If the AlN layer thickness is increased to improve anti-diffusion effect, then element diffusion is suppressed, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent specifies an optimized thickness range for the AlN intermediate layer (1 nm to 10 nm). This parameter optimization ensures sufficient diffusion barrier functionality while minimizing the increase in device complexity and manufacturing difficulty. The specific thickness range balances anti-diffusion effectiveness with structural simplicity.
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 anti-diffusion layer effectively prevents the diffusion of Ga and Mg elements, maintaining device characteristics equivalent to those without a cap layer, while reducing reverse leakage current to 1 nA or less, even when a cap layer is present, thus enhancing the reliability of semiconductor elements and PN junction diodes.
Implementation Method 1
an anti-diffusion layer made of AlN... the AlN layer serves as an anti-diffusion layer to prevent element diffusion
Data Source
AI summary
Provided is an epitaxial substrate for use in a semiconductor element, having excellent characteristics and capable of suitably suppressing diffusion of elements from a cap layer. An epitaxial substrate for use in a semiconductor element, in which a group of group-III nitride layers are laminated on a base substrate such that a (0001) crystal plane of the group of group-III nitride layers is substantially in parallel with a substrate surface of the base substrate, includes: a channel layer made of a first group-III nitride having a composition of Inx1Aly1Gaz1N (x1+y1+z1=1, z1>0); a barrier layer made of a second group-III nitride having a composition of Inx2Aly2N (x2+y2=1, x2>0, y2>0); an anti-diffusion layer made of AlN and having a thickness of 3 nm or more; and a cap layer made of a third group-III nitride having a composition of Inx3Aly3Gaz3N (x3+y3+z3=1, z3>0).