GaN and SiC have been unanimously recognized as the best materials for next generation power electronic devices, due to the superior material properties compared to conventional silicon, which enable higher power handling capability, higher operating temperatures, higher conversion efficiency, and higher electron mobility.
Despite the obvious benefits of GaN- and SiC-based power components, challenges still do exist, such as high interface trap density which leads to “current collapse” phenomenon (GaN), low inversion channel mobility (SiC), gate leakage current (GaN), poor threshold voltage stability (both GaN and SiC), and gate insulation and surface passivation (GaN).
ALD technology offers superior solutions to these challenges. Deposition of defect-free high-k dielectric layer is the key requirement for reducing gate leakage current, increasing inversion channel mobility, and improving threshold voltage stability. ALD stands superior here compared to other methods such as PECVD. With ALD, the highest quality ultra-thin, defect-free coatings of unmatched conformality, sharp interfaces, digitally repeatable thickness control and exact chemical composition can be produced. ALD process runs at moderate temperatures and from gaseous precursors so it is gentle also on sensitive substrates. Several ALD materials such as Al2O3, AlN, and ZrO2 have been shown to significantly improve the properties of power electronic components.
ALD deposited, high permittivity, large bandgap insulators such as Al2O3, HfO2, and SiO2 decrease interface trap density and improve the performance of both GaN- and SiC-based power components.
Normally-off HEMT devices with positive threshold voltage (e.g. recessed hybrid MISHEMTs and p-GaN gate devices) are important for the large scale adoption of the promising GaN material in practical applications. In these devices, efficient gate insulation and surface passivation are particularly critical in achieving optimal performance. ALD materials such as Al2O3, AlN, and HfSiO have excellent conformality and properties to make normally-off HEMT devices a viable technology for large scale utilization.
Also metals and other conductive materials can be deposited with ALD. In normally-off p-GaN HEMT devices, Schottky metal gates have shown superior performance compared to Ohmic gates in terms of higher threshold voltage and lower leakage current.
Picosun provides a large library of turn-key, production-proven solutions for deposition of high quality ALD dielectrics and other materials with equipment specifically designed and optimized for up to 200 mm wafer size, such as utilized in power component industries. Picosun’s ALD equipment and solutions are currently in production use at several prominent power device manufacturers in Europe, USA, and Asia.