SiC Nitride Epitaxial Structure for Stable 2DEG HEMTs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional nitride semiconductor HEMTs face challenges due to lattice mismatch-induced polarization, leading to inefficiencies in two-dimensional electron gas formation and channel control, particularly in devices using Si substrates.
Innovation Solution
A nitride semiconductor device is developed using an SiC substrate with a hexagonal crystal system, featuring a nitride epitaxial layer with a specific off-angle orientation and a semi-insulating nitride layer to suppress leak currents, along with a buffer layer to manage lattice strain, enabling the formation of a two-dimensional electron gas for improved HEMT performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a Si substrate is used for nitride semiconductor HEMT, then manufacturing cost is reduced, but lattice mismatch-induced polarization causes inefficiencies in two-dimensional electron gas formation and channel control
Solution Approach 1:
An AlN buffer layer is introduced as an intermediary between the Si substrate and the GaN-based nitride semiconductor layers. This buffer layer mediates the lattice mismatch between Si and GaN, reducing polarization effects and improving two-dimensional electron gas formation efficiency while allowing the use of cost-effective Si substrates
2Reliability
If lattice mismatch is present between GaN and AlGaN, then heterojunction is formed for electron supply, but polarization disrupts channel control and HEMT performance
Solution Approach 1:
The AlN buffer layer is strategically positioned at the interface between the Si substrate and the GaN layers, providing localized compensation for lattice mismatch and polarization effects. This local intervention maintains the necessary heterojunction properties for electron supply while improving channel control in the active region
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 enhances the formation and control of a two-dimensional electron gas, resulting in improved HEMT performance by optimizing the nitride semiconductor structure, which addresses the inefficiencies caused by lattice mismatch and polarization, leading to a more reliable and efficient normally-on HEMT operation.
Implementation Method 1
Due to polarization caused by lattice mismatch of GaN and AlGaN, a two-dimensional electron gas is formed at a position inside the electron transit layer that is only a few Å inward from an interface between the electron transit layer and the electron supply layer
Data Source
AI summary
A nitride semiconductor device 1 includes an SiC substrate 2 of a hexagonal crystal system that has a first main surface 2a and a second main surface 2b at an opposite side thereof and a nitride epitaxial layer 20 that is formed on the first main surface 2a and the first main surface 2a has an off angle of greater than 1° with respect to a c-plane of the hexagonal crystal.