Nitride Semiconductor Device With Indium Aluminum Gallium Nitride Back Barrier
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Solution Overview
Problem
Nitride semiconductor devices with gallium nitride (GaN) channel layers laminated on aluminum gallium nitride (AlGaN) back barrier layers face challenges in achieving high threshold voltage while maintaining crystal quality due to increased lattice mismatch and defects, leading to higher power consumption and reduced electron mobility.
Innovation Solution
A nitride semiconductor device structure is implemented with a back barrier layer of indium aluminum gallium nitride (InAlGaN) to reduce lattice mismatch with the GaN channel layer, allowing for uniform formation and improving threshold voltage by adjusting the composition of aluminum and indium to approximate the lattice constant of GaN, thereby enhancing crystal quality and reducing ON resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the aluminum composition of the back barrier layer is increased to improve threshold voltage, then the threshold voltage is improved, but the lattice mismatch rate between the back barrier layer and the channel layer becomes higher
Solution Approach 1:
The patent employs a composite back barrier layer structure consisting of multiple AlGaN layers with different aluminum compositions (x values). Specifically, it uses a first AlGaN layer with composition Alx1Ga(1-x1)N where 0.25 ≤ x1 ≤ 0.40, and a second AlGaN layer with composition Alx2Ga(1-x2)N where 0.40 < x2 ≤ 0.55. This composite structure allows the lower-Al-composition layer to provide a lattice-matched foundation for the GaN channel layer, while the higher-Al-composition layer provides the necessary threshold voltage improvement, thus resolving the contradiction between threshold voltage enhancement and lattice mismatch control.
2Manufacturing precision
If the lattice mismatch rate is reduced to improve crystal quality, then the crystal quality is improved, but the threshold voltage cannot be sufficiently improved
Solution Approach 1:
The patent applies local quality by creating spatial variation in aluminum composition within the back barrier layer. The first AlGaN layer with lower aluminum content (x1 = 0.25-0.40) is positioned adjacent to the GaN channel layer to ensure good lattice matching and high crystal quality. The second AlGaN layer with higher aluminum content (x2 = 0.40-0.55) is positioned farther from the channel layer to provide strong threshold voltage control. This local differentiation of material properties allows simultaneous achievement of high crystal quality at the critical interface and sufficient threshold voltage improvement in the bulk back barrier region.
3Reliability
If the crystal quality of the channel layer is deteriorated due to high lattice mismatch, then the electron mobility is decreased, but the threshold voltage can be improved
Solution Approach 1:
The patent introduces the first AlGaN layer with intermediate aluminum composition (x1 = 0.25-0.40) as a mediator between the second AlGaN layer with high aluminum composition (x2 = 0.40-0.55) and the GaN channel layer. This intermediate layer serves as a transition zone that gradually adjusts the lattice constant, reducing the abrupt lattice mismatch that would otherwise occur between the high-Al back barrier layer and the GaN channel layer. By providing this gradual transition, the mediator layer prevents the generation of excessive misfit dislocations and maintains high crystal quality at the channel layer, thereby preserving high electron mobility while still allowing the second layer to provide sufficient threshold voltage improvement.
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 device achieves improved threshold voltage and crystal quality, reducing ON resistance and power consumption while maintaining high electron mobility, making it suitable for high-speed and high-energy conversion applications.
Implementation Method 1
a lattice mismatch rate between the back barrier layer and the channel layer becomes higher. Accordingly, when the channel layer is laminated on the back barrier layer, crystal defect is easy to be introduced into the channel layer
Implementation Method 2
A nitride semiconductor has polarization resulting from symmetry of the crystal structure thereof, and it is known that a two-dimensional electron gas may be generated at a lamination interface of nitride semiconductor layers with different compositions of constituent elements
Data Source
AI summary
In one embodiment, a nitride semiconductor device is provided with a first semiconductor layer that is a layer of Alx1Ga(1-x1)N (0<x1≤1), a second semiconductor layer that is on the first semiconductor layer and is a layer of a nitride semiconductor Iny2Alx2Ga(1-x2-y2)N (0<x2<1, 0<y2<1, 0<x2+y2≤1) containing indium, a third semiconductor layer that is on the second semiconductor layer and is a layer of Alx3Ga(1-x3)N (0≤x3<1), and a fourth semiconductor layer that is on the third semiconductor layer and is an layer of Iny4Alx4Ga(1-x4-y4)N (0<x4<1, 0≤y4<1, 0<x4+y4≤1).