AlGaN Adjustment Layer for Semiconductor Crystallinity
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Solution Overview
Problem
Existing semiconductor devices with AlGaN-based thin films face challenges in achieving high crystal quality and flatness due to lattice mismatch and insufficient lattice relaxation, particularly when a nitride semiconductor layer with a different composition is formed on a buffer layer, leading to reduced crystallinity and flatness in the functional laminate.
Innovation Solution
Incorporating an AlzGa1-zN adjustment layer with p-type impurity between the buffer and the n-type AlxGa1-xN layer in the functional laminate, where the Al composition z is within ±0.05 of the Al composition x, to promote lateral growth and improve crystallinity and flatness, while also preventing impurity diffusion and strain-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an AlN low-temperature deposited buffer layer is formed between the buffer and the n-type AlGaN layer, then the buffer can be formed at lower temperature, but the lattice relaxation effect is reduced and crystallinity improvement is insufficient
Solution Approach 1:
An AlGaN adjustment layer with intermediate Al composition (0.05≤|x-z|≤0.2) is introduced between the AlN buffer layer and the n-type AlGaN functional layer. This intermediary layer acts as a transition zone that gradually changes the lattice constant, enabling effective lattice relaxation while maintaining the low-temperature deposition advantage of the AlN buffer.
Solution Approach 2:
The Al composition parameter is gradually changed from the AlN buffer layer (x=1) through the AlGaN adjustment layer (0.8≤x≤1) to the n-type AlGaN layer (0.3≤x≤0.7). This gradual parameter transition reduces the abrupt lattice mismatch, allowing the buffer to be deposited at low temperature while still achieving effective lattice relaxation and crystallinity improvement in the functional layer.
2Adaptability or versatility
If a nitride semiconductor layer with different composition is formed on the buffer, then the functional requirements can be met, but lattice mismatch occurs leading to reduced crystallinity and flatness
Solution Approach 1:
The adjustment layer is designed with specific local composition characteristics (Al composition x satisfying 0.8≤x≤1) that differ from both the buffer layer and the functional layer. This localized compositional quality creates a transition zone that specifically addresses the lattice mismatch problem at the buffer-functional layer interface, enabling the functional layer to have different composition while maintaining high crystallinity and flatness.
3Productivity
If the Al composition difference between buffer and functional layer is large, then the functional layer can have optimized composition for device performance, but the lattice mismatch increases causing strain and reduced quality
Solution Approach 1:
The structure is segmented into three distinct layers with different Al compositions: the AlN buffer layer (x=1), the AlGaN adjustment layer (0.8≤x≤1), and the n-type AlGaN functional layer (0.3≤x≤0.7). This segmentation allows each layer to be optimized for its specific function while the adjustment layer segment bridges the large composition difference, preventing lattice instability and strain.
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 AlzGa1-zN adjustment layer effectively passes improved crystallinity and flatness from the buffer to the functional laminate, enhancing light output and reducing impurity diffusion, resulting in a semiconductor device with superior optical and structural properties.
Implementation Method 1
a first semiconductor layer (buffer) mainly containing AlN or AlGaN that is doped with a lateral growth promoting substance is formed on a substrate
Implementation Method 2
lateral growth is promoted in the buffer, accompanied by promotion of coupling of dislocations, which allows the threading dislocation in a buffer surface to be reduced
Data Source
AI summary
To provide a semiconductor device including a functional laminate having flatness and crystallinity improved by effectively passing on the crystallinity and flatness improved in a buffer to the functional laminate, and to provide a method of producing the semiconductor device; in the semiconductor device including the buffer and the functional laminate having a plurality of nitride semiconductor layers, the functional laminate includes a first n-type or i-type AlxGa1-xN layer (0≦x<1) on the buffer side, and an AlzGa1-zN adjustment layer containing p-type impurity, which has an approximately equal Al composition to the first AlxGa1-xN layer (x−0.05≦z≦x+0.05, 0≦z<1) is provided between the buffer and the functional laminate.