AlGaN/GaN Heterostructure Mobility via AlN Exclusion Layer Removal
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Solution Overview
Problem
Al x Ga 1-x N/GaN heterostructures face limitations in achieving high mobility without the drawbacks of prior art structures, such as the need for an AlN exclusion layer, which increases surface potential and complicates obtaining a low ohmic contact, and result in trapping and lagging effects in high-frequency applications.
Innovation Solution
An Al x Ga 1-x N/GaN heterostructure is developed without an exclusion layer, featuring a sharp Al-content transition zone and optimized growth conditions to achieve a room temperature 2DEG mobility of 1800 to 2300 cm^2/Vs and a pinch-off voltage close to theoretical values, using Metal Organic Chemical Vapor Deposition (MOCVD) with precise control of precursor flows and growth parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an AlN exclusion layer is inserted between GaN and AlxGa1-xN layers to increase 2DEG mobility, then mobility improves to ~2200 cm²/Vs, but surface potential increases making low ohmic contact difficult to obtain
Solution Approach 1:
The invention removes the AlN exclusion layer from the heterostructure, extracting the problematic element that caused increased surface potential and contact resistance issues while maintaining the beneficial high mobility characteristics through optimized AlGaN layer composition and thickness
2Reliability
If an AlN exclusion layer is inserted to improve mobility, then 2DEG mobility increases, but device complexity increases due to additional recess etching requirements
Solution Approach 1:
By eliminating the AlN exclusion layer, the invention removes the need for additional recess etching steps in the contact metallization process, thereby reducing device complexity and manufacturing steps while maintaining high mobility performance
Solution Approach 2:
The invention optimizes the AlGaN barrier layer parameters (composition x, thickness) to achieve high mobility without requiring the AlN exclusion layer, changing the structural parameters to eliminate unnecessary processing steps
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 enhances 2DEG mobility and reduces trapping and lagging effects, enabling higher operation frequencies and improved device performance without the need for additional layers, while maintaining low pinch-off voltage and sheet resistance.
Implementation Method 1
using Metal Organic Chemical Vapor Deposition (MOCVD) with precise control of precursor flows and growth parameters
Data Source
Figure 1a~1b
Figure 2a~2c
Figure 3
AI summary
The present document discloses an AlxGa1-xN/GaN heterostructure, wherein x is 0.10<x<0.60, preferably 0.13<x<0.40, most preferably 0.15<x<0.25. The heterostructure comprises an AlxGa1-xN layer (14) formed directly on a GaN layer (13). The heterostructure presents a room temperature 2DEG mobility of 1800 to 2300 cm2/Vs, preferably 1900 to 2300 cm2/Vs, most preferably 2000 to 2300 cm2/Vs, and a pinch-off voltage which differs by 0.3 V or less, preferably by 0.25 V or less, most preferably by 0.20 V or less from a theoretical value of the pinch-off voltage, wherein the theoretical value of the pinch-off voltage is estimated based on an electrostatic band diagram obtained by XRD, of the AlxGa1-xN/GaN heterostructure.