GaN HEMT Epitaxial Structure With C Diffusion Blocking Layer
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Solution Overview
Problem
The existing GaN-based HEMT devices face reliability degradation and current collapse due to the easy diffusion of C atoms from the C-doped c-GaN high-resistance layer into the intrinsic u-GaN channel layer, which compromises the crystal quality and device performance.
Innovation Solution
A GaN-based HEMT device epitaxial structure is developed with a diffusion blocking layer, comprising a laminate or superlattice structure of Si3N4, AlN, and GaN layers, positioned between the C-doped c-GaN high-resistance layer and the intrinsic u-GaN channel layer, effectively blocking impurity diffusion and enhancing crystal growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a C-doped c-GaN high-resistance layer is used to achieve good electrical isolation performance, then off-set leakage is reduced and breakdown voltage is improved, but C atoms diffuse into the intrinsic u-GaN channel layer which reduces device reliability and causes current collapse
Solution Approach 1:
An AlN diffusion blocking layer is introduced as an intermediary between the C-doped c-GaN high-resistance layer and the intrinsic u-GaN channel layer. This AlN layer acts as a mediator that prevents C atoms from diffusing into the channel layer while maintaining the electrical isolation performance of the high-resistance layer, thereby eliminating the harmful effect of C atom diffusion without sacrificing reliability
Solution Approach 2:
The epitaxial structure is segmented into distinct functional layers with clear interfaces: the C-doped c-GaN high-resistance layer is separated from the intrinsic u-GaN channel layer by the AlN diffusion blocking layer. This segmentation creates a barrier that prevents the mixing of dopant atoms between layers, ensuring that the high-resistance layer provides electrical isolation while the channel layer maintains its intrinsic properties for high electron mobility
2Reliability
If intrinsic u-GaN channel layer is grown on C-doped c-GaN high-resistance layer to form AlGaN barrier layer/u-GaN channel layer/c-GaN high-resistance layer structure, then electrical isolation performance is improved, but C atom diffusion reduces device reliability and causes current collapse
Solution Approach 1:
The AlN diffusion blocking layer serves as a protective intermediary that stabilizes the composition of the intrinsic u-GaN channel layer by preventing C atom diffusion. This maintains the crystal quality and structural integrity of the channel layer while allowing the c-GaN high-resistance layer to provide its electrical isolation function
Solution Approach 2:
The AlN diffusion blocking layer is grown preliminarily before the intrinsic u-GaN channel layer to prevent C atom diffusion from occurring during subsequent growth and device operation. This preliminary protective action ensures that the channel layer maintains its intrinsic properties and high crystal quality throughout the device lifecycle
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 diffusion blocking layer effectively shields C atoms, improving device reliability and performance by maintaining high crystal quality and reducing current collapse, thereby achieving optimal doping and blocking effects.
Implementation Method 1
a diffusion blocking layer, comprising a laminate or superlattice structure of Si3N4, AlN, and GaN layers, positioned between the C-doped c-GaN high-resistance layer and the intrinsic u-GaN channel layer, effectively blocking impurity diffusion
Implementation Method 2
when using a metal organic chemical vapor deposition (MOCVD) method to obtain a specific C doping concentration, it is usually necessary to lower the growth temperature of GaN to implement self-doping, or to use a carbon source such as ethylene (C2H4) to implement external doping
Data Source
AI summary
The epitaxial structure sequentially includes from bottom to top a C-doped c-GaN high-resistance layer, a diffusion blocking layer, an intrinsic u-GaN channel layer, and an AlGaN barrier layer that are formed on a substrate. The diffusion blocking layer is a laminate structure or a superlattice structure; where the laminate structure comprises at least two layers selected from a group consisting of at least one Si3N4 layer, at least one AlN layer, and at least one GaN layer, and the laminate structure comprises at least one Si3N4 layer and also comprises at least one AlN layer or at least one GaN layer; where the superlattice structure is formed by periodically alternating laminate structures. The Si3N4 layer can block C atoms in the C-doped c-GaN high-resistance layer from diffusing into the intrinsic u-GaN channel layer. The AlN layer and the GaN layer provide growth transition for the diffusion blocking layer.