InAlGaN Capping Layer for Low-Resistance GaN Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional GaN-based transistors face complications in reducing source resistance and simplifying the electrode formation process, as they require alloy processing that degrades device characteristics and necessitates different materials for source/drain and gate electrodes.
Innovation Solution
A field effect transistor with a capping layer made of InAlGaN, allowing for non-alloy source and drain electrodes to be formed without annealing, using the same material for all electrodes, and incorporating a multilayered structure to reduce parasitic resistance and improve radio-frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alloy processing is performed to reduce contact resistance of ohmic electrodes, then contact resistance is reduced, but the fabrication process becomes complicated and device characteristics are degraded
Solution Approach 1:
The invention changes the material parameter of the capping layer from conventional GaN or AlGaN to InAlGaN with specific composition ratios (In: 5-20 at%, Al: 20-40 at%, Ga: 60-75 at%). This parameter change enables low contact resistance without requiring alloy processing, thus simplifying the fabrication process while maintaining reliable electrical contact
Solution Approach 2:
The InAlGaN capping layer serves as an intermediary between the metal electrode and the underlying GaN-based semiconductor layer. This intermediate layer with optimized composition provides both low contact resistance and prevents direct interaction between the metal and semiconductor, eliminating the need for complex alloy processing steps
2Reliability
If different materials are used for source/drain electrodes and gate electrode, then appropriate electrical characteristics are achieved, but the fabrication process becomes complicated
Solution Approach 1:
The InAlGaN capping layer provides universal compatibility with multiple electrode materials (Ti, Al, Ni, Pd, Pt, Au, etc.), enabling the same capping layer structure to support both ohmic contacts for source/drain electrodes and Schottky contacts for gate electrodes. This multi-functionality allows all electrodes to be formed using the same fabrication process without requiring different materials for different electrode types
Solution Approach 2:
By adjusting the composition parameters of the InAlGaN capping layer, the electrical characteristics can be tuned to achieve both low contact resistance for ohmic electrodes and appropriate Schottky barrier heights for gate electrodes, allowing universal electrode formation with a single material system
3Ease of manufacture
If conventional capping layers are used, then the fabrication process is simple, but contact resistance of ohmic electrodes cannot be sufficiently reduced
Solution Approach 1:
The invention optimizes the composition parameters of the capping layer by incorporating specific ratios of In (5-20 at%), Al (20-40 at%), and Ga (60-75 at%). This parameter optimization achieves sufficiently low contact resistance while maintaining a simple single-layer structure that is easy to fabricate, avoiding the complexity of multilayer structures
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 reduces contact resistance, simplifies the fabrication process, and enhances device characteristics, including radio-frequency performance, by using InAlGaN as the capping layer and allowing for simultaneous formation of ohmic and gate electrodes.
Implementation Method 1
a capping layer made of a compound represented by a general formula of InxAlyGa1−x−yN (wherein 0<x<1 and 0<y<1)
Implementation Method 2
a strong electric field is caused by polarization on the (0001) plane. Therefore, electrons are accumulated in a high density in the vicinity of the heterojunction interface in the GaN film, so as to generate the so-called two-dimensional electron gas (2DEG)
Data Source
AI summary
A field effect transistor includes a nitride semiconductor layered structure that is formed on a substrate and includes a capping layer made of a compound represented by a general formula of InxAlyGa1−yN (wherein 0<x≦1, 0≦y<1 and 0<x+y≦1). A non-alloy source electrode and a non-alloy drain electrode are formed on the capping layer so as to be spaced from each other.