Hydrogenated amorphous silicon germanium films doped with nitrogen (a-SiGe:H,N) to improve the long-wave infrared (LWIR) region absorption

Abstract

Sensors in the long-wave IR region are used due to their enormous importance in technology for a variety of applications, as medical diagnostics, fire protection, automotive night vision, security and military, among others. This paper reports our study of hydrogenated amorphous silicon-germanium (a-SiGe:H) thin films deposited by low-frequency plasma-enhanced chemical vapor deposition (LF-PECVD), in order to be used as long-wave infrared (LWIR) sensing films in microbolometers. In order to improve the absorbance of the IR sensing films, they were doped with nitrogen (N2) using different flow rates. FTIR measurements were performed to compare the absorption coefficient of the films doped with different N2 flow rates, where was observed that effectively, the absorption in the 8 – 14 μm spectral range was improved for the films deposited with larger N2 flow rates. Also, it was observed that the incorporation of N2 in the a-SiGe:H films improves the room temperature conductivity (σRT) up to 3 orders of magnitude.