Hetero-Substrate Defect Blocking Layer for Nitride Semiconductor
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Solution Overview
Problem
Nitride semiconductor thin films grown on hetero-substrates like sapphire or silicon carbide suffer from high crystal defects and strain due to lattice mismatch and thermal expansion differences, limiting their quality and efficiency in light emitting devices.
Innovation Solution
A hetero-substrate is manufactured with a base substrate, a buffer layer, a first nitride semiconductor layer, a defect blocking layer comprising metal droplets, and a second nitride semiconductor layer, where the metal droplets reduce dislocation density and internal strain by blocking threading dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitride semiconductor thin films are grown on hetero-substrates like sapphire or silicon carbide, then the substrate cost is reduced and manufacturing is simplified, but high crystal defects and strain occur due to lattice mismatch and thermal expansion differences
Solution Approach 1:
A buffer layer is introduced as an intermediary between the hetero-substrate and the nitride semiconductor thin film. This buffer layer serves as a transition zone that reduces the impact of lattice mismatch and thermal expansion differences, thereby decreasing threading dislocation density and crystal defects in the grown thin film while maintaining the use of cost-effective hetero-substrates
Solution Approach 2:
The buffer layer is prepared in advance before growing the nitride semiconductor thin film. By pre-establishing this intermediate layer with specific crystal structure and composition, the system preliminarily addresses the lattice mismatch issue, creating a more favorable growth environment for the subsequent thin film and reducing defect formation
2Manufacturing precision
If low-temperature gallium nitride and aluminum nitride buffers are used to reduce dislocation, then defect density is reduced to some extent, but the thin films still have high defect density of about 10^8 cm^-2
Solution Approach 1:
The buffer layer composition is optimized by adjusting the aluminum content in aluminum gallium nitride or using aluminum nitride, and the growth temperature is controlled at low temperatures (below 1000°C). These parameter changes enable better lattice matching and reduced thermal stress, achieving lower threading dislocation density (10^6 to 10^7 cm^-2) compared to conventional approaches
3Temperature
If nitride semiconductor thin films are cooled from high growth temperature to room temperature, then the device becomes operational, but tensile strain is applied to the thin film due to differences in coefficient of thermal expansion
Solution Approach 1:
The buffer layer is specifically designed to have thermal expansion properties that compensate for the mismatch between the hetero-substrate and the nitride semiconductor thin film. During cooling from growth temperature to room temperature, the buffer layer's thermal expansion characteristics reduce the tensile strain applied to the thin film, preventing crack formation and maintaining film integrity
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 reduces dislocation and defect density in nitride semiconductor thin films, improving the quality and reducing strain, which enhances the uniformity and efficiency of light emitting devices and prevents cracks in thick films.
Implementation Method 1
a defect blocking layer comprising a plurality of metal droplets, wherein the metal droplets reduce dislocation density and internal strain by blocking threading dislocations
Implementation Method 2
differences in lattice mismatch and coefficient of thermal expansion caused by the hetero-junction may cause high crystal defects and high strain in thin films
Implementation Method 3
subjecting a surface of the first semiconductor layer provided with the defect blocking layer to nitridation
Data Source
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AI summary
Disclosed is a nitride semiconductor. More specifically, disclosed are a hetero-substrate (100) and a method for manufacturing the same. The hetero-substrate (100) includes a base substrate (10), a buffer layer (20) disposed on the base substrate (10), a first semiconductor layer (30) disposed on the buffer layer (20), the first semiconductor layer (30) including a nitride semiconductor, a defect blocking layer (40) disposed on the first semiconductor layer (30), the defect blocking layer (40) including a plurality of metal droplets (41), and a second semiconductor layer (50) disposed on the defect blocking layer (40), the second semiconductor layer (50) including a nitride semiconductor.