Gallium Nitride (GaN) microLED technology continues setting new heights in the innovation of displays, offering high brightness—with some displays exceeding 10,000 pixels per inch (PPI), response time of approximately 0.2 nanoseconds, energy efficiency, and unmatched longevity of 10+ years. 

While demand for high-performance displays is surging, optimized fabrication for GaN microLED is required to meet industry standards. 

Now, the task is to solve technical issues in the material structure and scale the process up by using increasingly advanced techniques to enhance the quality and efficiency of GaN microLED devices.

According to the Verified Market Reports, the GaN microLED market, valued at $100.3 billion in 2023, is expected to grow to $450.77 billion by 2030. 

In this blog post, we take a look at the key strategies and challenges in GaN microLED fabrication, along with some real-world examples.

Key Techniques for GaN MicroLED Fabrication

The assembly of high-quality, effective designs that are efficient in optimizing the fabrication of GaN microLEDs can be achieved using the advanced methods described below:

Epitaxial Growth

One of the most common ways to achieve this is to use metalorganic chemical vapor deposition (MOCVD), as it is capable of depositing thin GaN layers on substrates precisely. 

AIXTRON and Veeco supply MOCVD systems, allowing manufacturers to grow GaN-based device epitaxial layers, including those for MicroLEDs. 

Notably, GaN microLEDs produced using Veeco’s state-of-the-art Propel GaN MOCVD system have achieved high reliability within the industry.

Chip Structuring

Chip structuring refers to the shaping of GaN microLEDs for optimal light extraction and reduced energy loss. This can be done using photolithography and dry etching, along with other microfabrication processes, to define the geometry of the LED.

Samsung MicroLED displays use advanced means to structure the chips that increase brightness and color accuracy. Besides that, Samsung has been able to use nanosheet structure to increase the surface area for light emission, which in turn enhances the overall efficiency.

Wafer Bonding

Wafer bonding becomes a critical technology to put GaN microLEDs together with other system components for overall enhanced thermal management as well as the overall electrical performance of the devices. 

GaN microLED wafers are finally bonded to silicon or sapphire substrates by direct bonding techniques or intermediate adhesives.

Sony adopted a hybrid bonding process where direct bonding was followed by silicon vias (TSVs) and, as a result, created high-density MicroLED arrays for its display panels. The process significantly enhances electrical and thermal conduction, which is vital in maintaining performance and lifespan in high-brightness display applications.

Key Challenges in the Fabrication of GaN MicroLED

Despite immense progress, many difficulties remain in making GaN microLED fabrication a commercial technology.

Material Defects 

• Among the chief concerns in the fabrication of MicroLEDs is material defects, particularly within the GaN layers. Such defects could result in reduced light output and might lead to poor efficiency of the microLEDs.

• Research conducted by the University of California, Santa Barbara, has worked on the reduction of threading dislocations in GaN by novel substrates and optimized growth conditions. Their effort has drastically mitigated these defects that disadvantage the performance of GaN-based microLEDs.

• Material defects have to be managed and eliminated during epitaxial growth for better performance of MicroLEDs. Most of them are challenges that require advanced knowledge of the epitaxial growth process.

Scalability Issues

• The main difficulties in scaling the production of GaN microLEDs towards commercial demand are maintaining quality while driving prices down. Current manufacturing processes are often time-consuming and expensive, therefore limiting GaN microLED scalability.

PlayNitride is one of the leading Taiwanese companies in the possibility of scaling MicroLED production. This corporation has developed several mass transfer processes for the accommodation of millions of GaN-based microLEDs onto large-area substrates, thus vital for the fabrication of large displays such as TVs.

• The main challenge of scaling GaN microLED production is delivering large-substrate yield and consistency. A fundamental shift is to ensure the scalability of these processes to deliver on large substrate needs, together with high-yielding eventual management systems.

Thermal Management

• Thermal management is critically vital for GaN microLEDs since overheating may compromise both performance and lifetime. With GaN microLED array sizes shrinking to a scale of very high pixel density, heat management will become an even more severe issue.

• In this view, the focal point of realization in thermal management would be integrating some working cooling solutions while at the same time not making the whole design bulky and too complex for a practical MicroLED solution.
  
  In other words, thermal management requires developing new materials and structures for effective heat dissipation concerning the thin display means.

• Aixtron, a leading company in semiconductor manufacturing, has been developing advanced thermal management solutions for GaN microLEDs. Their approach includes the use of high-efficiency heat sinks and innovative substrate materials that enhance heat dissipation without adding bulk to the device. 

Cost Efficiency

• High costs backing the advancement of GaN micro-LED manufacturing are one of the biggest barriers preventing mass availability. These costs are driven by the high prices of the starting materials used, unwieldy processes, and low yields of present manufacturing methods.

• UK MicroLED developer Plessey has enabled cost optimization by incorporating the GaN-on-Silicon technology, which is cheaper than the conventional GaN-on-Sapphire approach followed traditionally.
  
  This leads to material cost reduction, but, more importantly, with existing silicon manufacturing infrastructure, production expenditure is decreased.

Future Directions in GaN MicroLED Fabrication

The future of GaN microLED technology is promising with innovations in fabrication techniques:

Nanostructuring for Enhanced Performance

Research for nanostructuring techniques, including the addition of nanopillars and photonic crystals, to enhance light extraction for GaN microLEDs and increase their efficacy, is in progress. 

Innovations involving nanophotonic structures have significantly improved light extraction efficiency in GaN microLEDs. The research contributions from the University of Cambridge and Texas Tech University are particularly notable. 

Automation and AI 

The increasing need to integrate AI and automation into the fabrication process of GaN microLED production is for improved precision and reduced defectivity, but with better scalability. 

Aixtron has collaborated with Broadcom, National Research Council Canada, Optiwave, the University of Ottawa, and Fraunhofer ISE for the implementation of AI-based process control in MOCVD systems to optimize in-situ GaN growth conditions, an application that significantly helps reduce defect rates and promotes improved overall yields. 

GaN microLED Arrays on Flexible Graphene Substrates

Seoul National University and Sungkyunkwan University, Korea, have recently developed a method to produce high-quality LEDs on graphene and then integrate them into flexible microLED devices.

This breakthrough highlights the potential for integrating high-quality GaN MicroLEDs into flexible devices, offering enhanced performance while maintaining strong blue light emission.

Final Note

Looking ahead to the further development of the industry, addressing these challenges will be one of the major keys to unlocking GaN microLED technology to its full potential. 

Further research and development work in each of these areas brings with them very exciting prospects of even higher-resolution displays at improved efficiency and a lower cost of production. 

Overcoming these challenges will make MicroLED displays host applications in major industries as varied as consumer electronics, automotive, and augmented reality.