The IR camera for the Visible and Infrared Survey Telescope for Astronomy (VISTA) will have a sparse mosaic of 16 Raytheon VIRGO 2Kx2K HgCdTe detectors in its focal plane. All the 16 detectors have been individually tested in a custom built test facility at the UK ATC to confirm that their performance meets our specifications. This paper summarises the overall performance of all the detectors but also presents a detailed characterisation of a science detector in depth. In particular, we present important characteristics such as quantum efficiency, dark generation, read noise, well capacity and linearity, persistence, pixel operability and long term stability. We also discuss the precise estimation of the system gain and noise using both pixel-to-pixel (spatial) and temporal methods, read noise performance with multiple sampling, the apparent increase in the dark generation followed by reset, behaviour of reference pixels and our attempts to use these pixels to reduce low frequency noise.
