APPLICATIONS OF TECHNOLOGY:

• Transistors
• Solar cells
• Photodetectors operating in the ultraviolet to green portion of the spectrum
  
• Resonant tunneling devices
• Blue and white light emitting diodes
• Laser diodes
  

ADVANTAGES OVER GALLIUM NITRIDE GROWN DIRECTLY ON SILICON SUBSTRATES:

• Improved luminescence
  
• Fewer crystal defects

ADVANTAGES OVER GALLIUM NITRIDE GROWN ON SILICON WITH ALUMINUM NITRIDE BUFFER LAYERS:

• Superior diffusion resistance
  
• Closer lattice match with gallium nitride
  
• Metallic conductivity
  
• Mirror reflectivity

ADVANTAGES OVER GALLIUM NITRIDE GROWN ON SAPPHIRE OR SILICON CARBIDE:

• Larger wafer diameter
  
• Less expensive substrate wafers
  
• Better substrate thermal conductivity
  
• Compatibility with Si device technology

ABSTRACT:

Eicke Weber and colleagues at Berkeley Lab have grown gallium nitride films of excellent structural and optical quality on silicon substrates using a hafnium nitride (HfN) intermediate layer. The researchers have established the process parameters for the deposition of HfN on silicon as well as gallium nitride on HfN.

Growing gallium nitride on a silicon rather than a sapphire substrate offers considerable cost advantages and the possibility of monolithic integration of GaN-based devices with conventional Si electronics. However, growing GaN directly on silicon usually poses cracking and wetting problems. While these problems have been mitigated using aluminum nitride (AlN) buffer layers, AlN exacerbates interdiffusion at the surface. Because Si is a n-type dopant, this interdiffusion results in high unintentional doping levels in the film and the device area. Using novel diffusion-resistant HfN buffer layers on silicon, Robert Armitage and Eicke Weber have grown GaN films up to 1.2 µm thick with properties comparable to those grown on AlN buffers on silicon. Even better results are expected when the GaN deposition temperature and the HfN film deposition parameters are optimized. Additional advantages of the Berkeley Lab buffer material include a closer lattice match with gallium nitride, metallic conductivity, and mirror reflectivity.

STATUS:

• U.S. Patent #6,929,867 and other patents pending
• Available for licensing

REFERENCE NUMBER: IB-1800

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:

• Growth of GaN with a Low Density of Structural Defects, IB-1619
• Improved GaN MBE-Growth using Bismuth as a Surfactant, IB-1290

PUBLICATION:

Armitage, R., Yang, Q., Feick, H., Gebauer, J., Weber, E. R., "Lattice-Matched HfN Buffer Layers for Epitaxy of GaN on Si," Applied Physics Letters 2002, 81, 1450-1452