Nitride Semiconductor Growth for Defect Reduction
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Solution Overview
Problem
Nitride compound semiconductor devices, such as LEDs, face defects due to lattice mismatch when grown on sapphire substrates, which impair their properties, and existing substrate removal methods are inefficient, especially for reusing expensive substrates.
Innovation Solution
A method involving the growth of nitride compound semiconductor layers with specific structural and temperature conditions to form non-planar three-dimensional structures, followed by a planarizing layer, allowing for efficient substrate removal and the creation of coupling-out structures that enhance radiation characteristics, using metal organic vapor phase epitaxy (MOVPE) and laser lift-off or wet chemical processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitride compound semiconductor layers are heteroepitaxially grown onto sapphire substrates, then the device can be produced with standard manufacturing processes, but defects form in the semiconductor material due to lattice mismatch
Solution Approach 1:
A nucleation layer of aluminum nitride is introduced as an intermediary between the sapphire substrate and the gallium nitride semiconductor layers. This intermediate layer mediates the lattice mismatch between sapphire and GaN, reducing defect formation while maintaining compatibility with standard heteroepitaxial manufacturing processes
Solution Approach 2:
The patent modifies growth parameters during MOVPE processes, including temperature gradients and gas flow conditions, to control the formation and removal of the sapphire substrate. By changing these parameters, the process achieves both high-quality layer growth and substrate removal capability
2Ease of operation
If the sapphire growth substrate is removed using conventional methods, then the device can be transferred to a carrier, but the process is inefficient and substrate reuse is difficult
Solution Approach 1:
The patent replaces conventional mechanical substrate removal methods with a chemical etching process. The sapphire substrate is selectively etched using chemical solutions that dissolve the substrate material, enabling efficient removal and transfer of the semiconductor layers to a carrier while preserving the expensive sapphire substrates for reuse
Solution Approach 2:
The etching process selectively removes the sapphire substrate while leaving the gallium nitride device structure intact on a carrier. This enables recovery and reuse of the expensive sapphire substrates, improving productivity and reducing manufacturing costs
3Ease of manufacture
If a planar surface is maintained throughout growth, then manufacturing is simpler, but coupling-out of radiation is reduced
Solution Approach 1:
The patent transitions from maintaining a two-dimensional planar surface to developing three-dimensional pyramidal structures during the growth process. These 3D structures increase the surface area and improve radiation coupling efficiency by extracting light that would otherwise be trapped by total internal reflection at the planar interface
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 method reduces defect density in nitride compound semiconductor devices, enables efficient substrate reuse, and improves radiation characteristics by forming controlled coupling-out structures, leading to enhanced performance and cost-effectiveness in optoelectronic devices.
Implementation Method 1
The nucleation layer may be deposited by sputtering, for example.
Implementation Method 2
The first nitride compound semiconductor layer and the additional nitride compound semiconductor layers deposited in subsequent additional method steps are preferably epitaxially deposited, in particular by metal organic vapor phase epitaxy (MOVPE).
Implementation Method 3
The first nitride compound semiconductor layer and the additional nitride compound semiconductor layers deposited in subsequent additional method steps are preferably epitaxially deposited, in particular by metal organic vapor phase epitaxy (MOVPE).
Implementation Method 4
For removing the growth substrate from a nitride compound semiconductor device, in particular a per se known laser lift-off method can be used.
Data Source
AI summary
A method for procuring a nitride compound semiconductor device is disclosed. In an embodiment the method includes growing a first nitride compound semiconductor layer onto a growth substrate, depositing a masking layer, growing a second nitride compound semiconductor layer onto the masking layer, growing a third nitride compound semiconductor layer onto the second nitride compound semiconductor layer such that the third nitride compound semiconductor layer has non-planar structures and growing a fourth nitride compound semiconductor layer onto the non-planar structures such that the fourth nitride compound semiconductor layer has an essentially planar surface. The method further includes growing a functional layer sequence of the nitride compound semiconductor device, connecting a side of the functional layer sequence located opposite to the growth substrate to a carrier and removing the growth substrate.