Dilute nitride materials are the material system that enables photonic devices working at the optical telecommunication wavelengths of 1300 and 1550nm on a low cost GaAs platform instead of the incumbent InP substrates. This allows the devices to be developed on a more robust substrate type that is commercially available at a larger size. Until now, a suitable material for photoconductive (PC) switching at 1550nm wavelength does not exist. In this project, we propose to use novel dilute nitride material, GaNAsSb, for ultra-fast photoconductive switch designed to work at 1550nm optical communication wavelengths. This project aims to solve key technical challenges to obtain high dark resistivity and sub-picosecond carrier lifetime, and to improve the ON/OFF ratio and bandwidth. The project will be divided into two sequential phases; Phase I being the material growth and characterization and Phase II the PC switch device development and characterization. Note that the different core abilities of the Singapore and French teams allow these project phases to be developed in parallel should the need arises. The objective of Phase I is to control the epitaxy processes to obtain suitable GaNAsSb properties for photoconductive switch application such as suitable bandgap energy, (sub)picosecond carrier lifetime, and high dark resistivity towards 1M?.cm. This is mainly achieved by tuning the GaNAsSb substrate temperature and the flux ratio of group V/III elements during growth to optimize the formation of arsenic antisites. In Phase II, a series of device wafers based on the results of Phase I will be grown, fabricated and characterized. The objective of Phase II is to optimize the fabrication procedures and to conduct ON/OFF ratio and bandwidth measurement on the PC switch devices under 1550nm laser excitation. PC switch with low contact resistance to minimize insertion loss will improve ON/OFF ratio towards 40dB and high bandwidth beyond 20GHz. If the project is successful, the photoconductive switch developed here will be an important component in optical communication, particularly in microwave switching and signal sampling. The 1550nm PC switch technology may also be applied to other applications such as terahertz detection/generation.