Group III Nitride Semiconductor Buffer Layer for Sapphire Substrates
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Solution Overview
Problem
The challenge lies in stably obtaining a group III nitride compound semiconductor crystal with good crystallinity on substrates like sapphire and SiC, due to large lattice mismatches and the inefficiencies of existing buffer layer growth methods, which result in poor crystallinity and device performance.
Innovation Solution
A group III nitride compound semiconductor stacked structure is developed, featuring a first layer with columnar crystals of controlled density and width, grown using plasma-activated sputtering, followed by a second layer grown via MOCVD or reactive sputtering, ensuring a low-dislocation, high-crystallinity surface suitable for LED and other semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-temperature buffer layer composed of AlN or AlGaN is deposited on the substrate using MOCVD, then the buffer layer can be formed to enable subsequent high-temperature epitaxial growth, but the crystallinity of the buffer layer is poor due to large lattice mismatch
Solution Approach 1:
The invention changes the growth method from MOCVD to sputtering, and changes the growth temperature from low temperature to high temperature (700-900°C), which fundamentally alters the crystallization behavior and enables formation of buffer layers with good crystallinity despite large lattice mismatch
Solution Approach 2:
The invention utilizes the phase transition characteristics of group III nitride compounds during sputtering deposition, where the high-energy plasma environment and high substrate temperature promote proper crystalline phase formation and reduce defects caused by lattice mismatch
2Productivity
If MOCVD method is used to grow the buffer layer, then high growth rate can be achieved, but the uniformity and quality of columnar crystal structure is poor
Solution Approach 1:
The invention replaces the chemical vapor deposition mechanism of MOCVD with the physical sputtering mechanism, where plasma-activated metal raw materials are deposited onto the substrate. This substitution enables better control over crystal structure formation and columnar crystal uniformity
3Reliability
If DC sputtering is used to film-form the buffer layer at high temperature, then good crystal can be obtained, but the process complexity and time consumption increase
Solution Approach 1:
The invention employs periodic or pulsed sputtering modes where the sputtering process is interrupted by annealing steps. This periodic action allows the buffer layer to be formed and then thermally treated to improve crystallinity, achieving good crystal quality while managing process time efficiently
Solution Approach 2:
The invention performs preliminary formation of the buffer layer structure through sputtering, followed by in-situ annealing treatment. This preliminary action creates a foundation that can be subsequently improved through thermal treatment, reducing the need for multiple separate processing steps
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
This approach enables the production of semiconductor devices with improved crystallinity and performance, such as LEDs, by effectively utilizing a columnar crystal buffer layer to enhance the growth of subsequent nitride layers, leading to better light-emitting properties and durability.
Implementation Method 1
a first layer containing a columnar crystal with a definite crystal interface and having a columnar crystal density of from 1×10³ to 1×10⁵ crystals/μm² when viewed from a planar direction is formed on a substrate by a method of activating a group III metal raw material and a nitrogen element-containing gas with a plasma to cause a reaction therebetween
Implementation Method 2
a method of activating a group III metal raw material and a nitrogen element-containing gas with a plasma to cause a reaction therebetween
Implementation Method 3
epitaxially growing a group III nitride compound semiconductor crystal on a sapphire substrate by the metal-organic chemical vapor deposition (MOCVD) method
Data Source
AI summary
An object of the present invention is to obtain a group III nitride compound semiconductor stacked structure where a group III nitride compound semiconductor layer having good crystallinity is stably stacked on a dissimilar substrate.The group III nitride compound semiconductor stacked structure of the present invention is a group III nitride compound semiconductor stacked structure comprising a substrate having provided thereon a first layer comprising a group III nitride compound semiconductor and a second layer being in contact with the first layer and comprising a group III nitride compound semiconductor, wherein the first layer contains a columnar crystal with a definite crystal interface and the columnar crystal density is from 1×103 to 1×105 crystals/μm2.