Boron-doped hydrogenated mixed-phase silicon as thermo-sensing films for infrared detectors

Silicon materials have been widely used as thermo-sensing layers in infrared detectors or uncooled micro-bolometers. Parameters such as a large thermal coefficient of resistance (TCR), low sheet resistance (R-s), and low 1/ f noise are important for high performance of these devices. However, there is always a trade-off between these parameters. For example, the crystalline silicon materials typically exhibit low R-s and 1/f noise, and significantly low TCR, while the amorphous silicon materials generally have large TCR, and considerably high Rs and 1/ f noise. Consequently, the best trade-off can be achieved by using a mixed-phase structure of silicon materials, i. e. an intermediate form between the crystalline and amorphous structures. Herein we report the important characteristics of hydrogenated mixed-phase silicon films, deposited by the plasma-enhanced chemical vapour deposition process, for infrared detectors. The films in the mixed-phase structure showed high TCR values in the range of 2-3% K-1 and moderate sheet resistances in range of 10-40 M Omega sq(-)1. These results indicate that the mixed-phase silicon films are potential alternatives to conventional boron doped hydrogenated amorphous and microcrystalline silicon films for use as thermo-sensing layers in infrared detectors.