  MOSFIRE is a new multi-object near-infrared spectrometer for the Keck 1
telescope with a spectral resolving power of R 3500 for a 0.7" slit (2.9
pixels). The detector is a substrate-removed 2K x 2K HAWAII 2-RG HgCdTe array
from Teledyne Imaging Sensors with a cut-off wavelength of 2.5 {\mu}m and an
operational temperature of 77K. Spectroscopy of faint objects sets the
requirement for low dark current and low noise. MOSFIRE is also an infrared
camera with a 6.9' field of view projected onto the detector with 0.18" pixel
sampling. Broad-band imaging drives the requirement for 32-channel readout and
MOSFIREs fast camera optics implies the need for a very flat detector. In this
paper we report the final performance of the detector selected for MOSFIRE. The
array is operated using the SIDECAR ASIC chip inside the MOSFIRE dewar and v2.3
of the HxRG software. Dark current plus instrument background is measured at
<0.008 e- s-1 pixel-1 on average. Multiple Correlated Double Sampling (MCDS)
and Up-The-Ramp (UTR) sampling are both available. A read noise of <5e- rms is
achieved with MCDS 16 and the lowest noise of 3e- rms occurs for 64 samples.
Charge persistence depends on exposure level and shows a large gradient across
this detector. However, the decay time constant is always \sim 660 seconds.
Linearity and stability are also discussed.
