Ga-containing Group III Nitride Semiconductor Buffer Layer
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Solution Overview
Problem
Existing methods for growing Ga-containing group III nitride semiconductors on sapphire substrates fail to effectively reduce threading dislocation density due to small crystal nuclei and high dislocation origin density, leading to inadequate semiconductor quality.
Innovation Solution
A method involving the formation of a buffer layer in a polycrystal, amorphous, or mixed state of polycrystal and amorphous on the substrate, followed by heat treatment at a temperature higher than the growth temperature of single crystal Ga-containing group III nitride semiconductors to reduce crystal nucleus density, and subsequent growth using MOCVD, resulting in larger crystal nuclei and reduced threading dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a low temperature buffer layer of ultra thin GaN is formed and temperature is increased to grow GaN fine crystals, then GaN facet growth is achieved, but crystal nuclei remain small and threading dislocation density remains high
Solution Approach 1:
The patent applies preliminary action by forming a buffer layer in a specific polycrystal/amorphous mixed state before GaN growth, then performing heat treatment to reduce crystal nucleus density. This preliminary preparation of the buffer layer structure enables subsequent GaN growth with reduced threading dislocation density, addressing the contradiction between achieving facet growth and reducing dislocation density.
Solution Approach 2:
The patent changes physical parameters by controlling the buffer layer formation temperature and composition to create a polycrystal/amorphous mixed state, then applying heat treatment at specific temperatures to reduce crystal nucleus density. These parameter changes transform the buffer layer structure to enable reduced threading dislocation density while maintaining GaN growth quality.
2Ease of manufacture
If an AlN buffer layer is formed by MOCVD at low temperature, then the buffer layer provides initial growth surface, but the crystal nuclei density remains high leading to frequent threading dislocation occurrence
Solution Approach 1:
The patent changes manufacturing parameters by forming the AlN buffer layer at low temperature (300-600°C) in a polycrystal/amorphous mixed state, then applying heat treatment to reduce crystal nucleus density. This parameter change strategy enables easy buffer layer formation while subsequently reducing threading dislocation density through controlled heat treatment.
Solution Approach 2:
The patent utilizes phase transitions by forming the buffer layer in a polycrystal/amorphous mixed state and then applying heat treatment to induce structural changes that reduce crystal nucleus density. This phase transition approach transforms the buffer layer from a high-nucleus-density state to a state suitable for reduced threading dislocation growth.
3Manufacturing precision
If the substrate temperature is increased to grow GaN single crystal, then high quality GaN growth is achieved, but crystal nuclei become too dense and cause high threading dislocation density
Solution Approach 1:
The patent applies preliminary action by first forming a buffer layer in a polycrystal/amorphous mixed state and performing heat treatment to reduce crystal nucleus density before initiating GaN single crystal growth. This preliminary preparation ensures that when high temperature growth begins, the underlying buffer layer has reduced nucleus density, enabling both high crystal quality and reduced threading dislocation density.
Solution Approach 2:
The patent applies local quality by creating different structural states in different regions: the buffer layer is maintained in a polycrystal/amorphous mixed state with reduced crystal nucleus density, while the GaN layer grows as high-quality single crystal. This local differentiation enables simultaneous achievement of easy manufacture and high reliability.
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 method significantly decreases the threading dislocation density in the semiconductor by forming larger crystal nuclei, enhancing the lattice conformity and reducing grain boundary dislocations, thereby improving the quality of the grown Ga-containing group III nitride semiconductors.
Implementation Method 1
heat-treating the substrate having the buffer layer formed thereon at a temperature higher than a temperature at which a single crystal of a Ga-containing group III nitride semiconductor grows on the buffer layer and at a temperature that the Ga-containing group III nitride semiconductor does not grow, to reduce crystal nucleus density of the buffer layer
Implementation Method 2
growing the Ga-containing group III nitride semiconductor on the buffer layer by an MOCVD method
Data Source
AI summary
A method for producing a Ga-containing group III nitride semiconductor having reduced threading dislocation is disclosed. A buffer layer in a polycrystal, amorphous or polycrystal/amorphous mixed state, comprising AlGaN is formed on a substrate. The substrate having the buffer layer formed thereon is heat-treated at a temperature higher than a temperature at which a single crystal of a Ga-containing group III nitride semiconductor grows on the buffer layer and at a temperature that the Ga-containing group III nitride semiconductor does not grow, to reduce crystal nucleus density of the buffer layer as compared with the density before the heat treatment. After the heat treatment, the temperature of the substrate is decreased to a temperature that the Ga-containing group III nitride semiconductor grows, the temperature is maintained, and the Ga-containing group III nitride semiconductor is grown on the buffer layer.