Ultra-thin SiNx in superlattice via nitridation of a-Si in-situ hot wire chemical vapor deposition

• Ultra thin SiNx is fabricated by hot wire chemical vapor deposition.
• SiNx layer of thickness ~ 1.9 nm is formed via nitridation of a-Si layer at 250 °C.
• Ultra thin SiNx layers are realized in superlattice films of quantum wells and quantum dots.

The fabrication of ultra-thin SiNx (< 2 nm) is a necessary step in third generation photovoltaics, memory, or light-emitting diode applications. Using the low temperature, cheap, scaleable synthesis technique of hot-wire chemical vapor deposition (HWCVD) for this purpose poses many challenges. Here, an approach of fabricating ultra thin SiNx of thickness ~ 1.9 nm in a superlattice (SL) structure via nitridation of a-Si layers in-situ HWCVD at 250 °C is reported. Quantum well SL and quantum dot (QD) SL films are realized, wherein SiNx layers are formed by nitriding a-Si. Both these films investigated by Raman spectroscopy and high resolution transmission electron microscopy, reveal the formation of ultra-thin SiNx in a SL structure with a-Si, accompanied by sharp interfaces. In addition, annealing of the SL structures, results in QDs of crystalline Si in the a-Si layers, maintaining the SiNx layer as well as the sharp interface between the SiNx and a-Si layers of the as-deposited SL structure.