PVD Aluminum Nitride Buffer Layers for GaN LED Fabrication
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Solution Overview
Problem
The fabrication of gallium nitride-based light emitting diodes (LEDs) using group III-nitride materials often faces challenges such as defect formation and crack issues due to sensitivity to process conditions, particularly when growing these materials on foreign substrates, and the inclusion of buffer layers is not straightforward, leading to inefficiencies in the fabrication process.
Innovation Solution
The use of physical vapor deposition (PVD) formed aluminum nitride (AlN) buffer layers, which are pre-treated and deposited using reactive sputtering in a PVD chamber, providing an atomically smooth surface and improved crystalline orientation, thereby reducing the thermal budget and enabling faster deposition rates and improved crystalline quality of gallium nitride layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional buffer layers are used in heteroepitaxy of group III-V materials, then defect formation is reduced, but the fabrication process becomes more complex and time-consuming
Solution Approach 1:
The invention changes the material parameter by using aluminum nitride (AlN) instead of conventional gallium nitride (GaN) buffer layers. AlN has different lattice constants and thermal expansion coefficients that reduce misfit dislocations and defect formation during heteroepitaxial growth of GaN layers on foreign substrates like sapphire or silicon
Solution Approach 2:
The AlN buffer layer is deposited beforehand using physical vapor deposition (PVD) sputtering to prepare the substrate surface before subsequent chemical vapor deposition (CVD) of GaN layers. This preliminary action creates an atomically smooth surface with improved crystalline orientation that facilitates defect-free growth of subsequent layers
2Manufacturing precision
If multiple buffer layers and process steps are used to achieve smooth surfaces and proper orientation, then material quality is improved, but deposition time and throughput are reduced
Solution Approach 1:
The invention combines the functions of multiple buffer layers into a single AlN buffer layer that simultaneously provides surface smoothing, crystalline orientation control, and defect reduction. The PVD sputtering process deposits the AlN layer in a single continuous step, eliminating the need for multiple separate deposition processes and intermediate annealing steps
Solution Approach 2:
The invention replaces conventional CVD-based buffer layer deposition with PVD sputtering. PVD offers faster deposition rates and better control over film density and stoichiometry, achieving atomically smooth surfaces and improved crystalline orientation more quickly than traditional CVD methods
3Temperature
If conventional buffer layer processes are used, then thermal management is adequate, but the thermal budget increases and affects subsequent processing
Solution Approach 1:
The invention changes the thermal parameter by using AlN, which has superior thermal conductivity compared to GaN buffer layers. This allows for more efficient heat dissipation from the LED active region, reducing the overall thermal budget and enabling lower processing temperatures in subsequent fabrication 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 enhances the throughput of LED fabrication, reduces defectivity, and simplifies the process by eliminating the need for oxide removal operations and reducing the thickness of the device layer, while achieving improved crystalline quality and material alignment, resulting in a 50% throughput improvement and enhanced device performance.
Implementation Method 1
reactive sputtering an aluminum nitride (AlN) layer on the surface of the substrate from an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-based gas or plasma
Implementation Method 2
physical vapor deposition (PVD) formed aluminum nitride buffer layers
Data Source
AI summary
Fabrication of gallium nitride-based light devices with physical vapor deposition (PVD)-formed aluminum nitride buffer layers is described. Process conditions for a PVD AlN buffer layer are also described. Substrate pretreatments for a PVD aluminum nitride buffer layer are also described. In an example, a method of fabricating a buffer layer above a substrate involves pre-treating a surface of a substrate. The method also involves, subsequently, reactive sputtering an aluminum nitride (AlN) layer on the surface of the substrate from an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-based gas or plasma.