InAlGaN Barrier Layer Epitaxial Substrate for HEMT 2DEG Optimization
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Solution Overview
Problem
Conventional AlGaN/GaN heterostructure-based high electron mobility transistors (HEMTs) face challenges in achieving high two-dimensional electron gas concentration and mobility due to tensile stress and surface morphology issues, leading to deteriorated contact characteristics and device dynamics.
Innovation Solution
An epitaxial substrate with a multi-layered structure comprising a GaN channel layer, an AlpGa1−pN spacer layer, and an InxAlyGazN barrier layer, where the composition of the barrier layer is optimized within specific ranges on a ternary phase diagram to enhance two-dimensional electron gas concentration and mobility, while reducing contact resistance and gate leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the AlN mol fraction in AlGaN barrier layer is increased to increase two dimensional electron gas concentration, then the two dimensional electron gas concentration is improved, but tensile stress inside the barrier layer becomes larger causing film quality deterioration and surface morphology aggravation
Solution Approach 1:
The invention changes the compositional parameters of the barrier layer by introducing InAlGaN quaternary mixed crystal with specific composition ratios (0.03≤x≤0.15, 0.15≤y≤0.45, 0.40≤z≤0.80), which modifies the tensile stress characteristics and band structure to simultaneously achieve high two dimensional electron gas concentration and maintain film quality
Solution Approach 2:
The invention uses InAlGaN quaternary mixed crystal as a composite material combining InN, AlN, and GaN components in specific proportions, creating a barrier layer that balances high electron gas concentration with reduced tensile stress and improved surface morphology
2Reliability
If InAlGaN quaternary mixed crystal is used for the barrier layer to control tensile stress and band structure, then electrical characteristics are improved, but two dimensional electron gas mobility remains low due to inappropriate composition ratio and growth condition
Solution Approach 1:
The invention optimizes the compositional parameters (x, y, z) of InAlGaN barrier layer and growth conditions (temperature, pressure, V/III ratio) to simultaneously improve electrical characteristics and two dimensional electron gas mobility, achieving mobility≥1300 cm2/Vs
3Quantity of substance
If AlGaN barrier layer with large AlN mol fraction is used to increase two dimensional electron gas concentration, then the two dimensional electron gas concentration is improved, but contact characteristics (ohmic characteristic, Schottky characteristic) are deteriorated
Solution Approach 1:
The invention changes the barrier layer composition to InAlGaN with optimized Al content (0.15≤y≤0.45) and adds In content (0.03≤x≤0.15), which reduces tensile stress and improves contact characteristics while maintaining high two dimensional electron gas concentration
4Quantity of substance
If AlGaN barrier layer with large AlN mol fraction is used to increase two dimensional electron gas concentration, then the two dimensional electron gas concentration is improved, but surface level increases causing deterioration of device dynamic characteristics
Solution Approach 1:
The invention optimizes the barrier layer composition parameters (x, y, z) and growth conditions to reduce surface level while maintaining high two dimensional electron gas concentration, achieving smooth surface morphology with RMS roughness≤0.5 nm
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 optimized epitaxial substrate achieves higher two-dimensional electron gas concentration and mobility, improved contact characteristics, and reduced gate leakage current, meeting stringent device criteria for practical HEMT device performance.
Implementation Method 1
generating a two dimensional electron gas (2DEG) having high concentration in a lamination interface (heterointerface) by large polarization effect (spontaneous polarization effect and piezo polarization effect) specific to nitride material
Implementation Method 2
epitaxially forming a channel layer made of GaN on a base substrate; epitaxially forming a spacer layer made of group III nitride
Data Source
AI summary
An epitaxial substrate having preferable two dimensional electron gas characteristic and contact characteristic is provided in the present invention. A channel layer is formed on a base substrate with GaN. A spacer layer is formed on the channel layer with AlN. A barrier layer is formed on the spacer layer with group III nitride having a composition of InXAlyGazN (wherein x+y+z=1) and at least including In, Al, and Ga such that the composition of the barrier layer is within the range surrounded with four lines defined in accordance with the composition on a ternary phase diagram with InN, AlN, and GaN as vertexes.