Sputter epitaxy for III-V power electronics

Magnetron sputter epitaxy (MSE, or sputter epitaxy for short) is a pioneering technology for the deposition of III-nitride semiconductors such as aluminum nitride (AlN) and gallium nitride (GaN). III-nitride semiconductors are the basis for future high-performance electronic components in applications such as power electronics, high-frequency technology and optoelectronics.
The unique properties of AlN and GaN are high electron mobilities, high thermal conductivities, good thermal and chemical stabilities, very large band gaps and high electric field strengths. These properties are crucial for the efficiency and performance of power electronic devices such as HEMTs (high-electron-mobility transistors), vertical transistors, diodes and LEDs, as they enable improved heat dissipation, higher dielectric strength, faster switching speeds and higher quantum yields.

Sputterepitaxy is a form of physical vapor deposition (PVD) in which atoms are evaporated from a target surface and deposited in a controlled manner on a substrate. This technique enables the precise production of epitaxial (crystalline), semiconducting thin films with specific electrical and optical properties suitable for a wide range of applications.
Sputter epitaxy enables precise control over layer properties and allows the production of high-quality, high-performance electronic components, which are crucial for the growing demands of power electronics and wireless communication.

Current research at the Fraunhofer FEP is focused on controlling morphology, crystal quality (epitaxy), and polarity in III-nitride layers, particularly through the use of aluminum nucleation layers. Important findings include:

• Improvement of crystal quality: X-ray diffraction measurements show that the use of Al nucleation layers significantly improves the crystal quality of the AlN and GaN layers.
  
• Morphology and polarity: Nanoscale structural and chemical investigations using scanning transmission electron microscopy (STEM) show that Al nucleation influences the polarity of the AlN layers. This enables the targeted production of both metal-polar and N-polar layers on a macroscopic scale.
  
• Technological relevance: Controlling layer polarity is an important technological milestone for the development of even more efficient electronic components of the next generation.

In the future, innovative processes will be developed at the Fraunhofer FEP to further increase the efficiency and quality of sputter processes and heteroepitaxial layers and to adapt them to industry requirements. In particular, nitride epitaxy is to be made possible on wafer diameters of up to 200 mm.

Sputter epitaxy allows for a more resource- and energy-efficient production of nitride semiconductors compared to conventional methods such as MOCVD (metal organic chemical vapor deposition) and contributes significantly to the further development of III-nitride technology. Sputter epitaxy opens up new perspectives for the application of nitride semiconductors in power electronics, in particular for power converters, power amplifiers, and optoelectronic components.