In order to study the temperature-dependent photoelectric characteristics of the extended wavelength In0.8Ga0.2As PIN infrared detectors, based on planer process with sealed-ampoule diffusion method, front-illuminated 256×1 linear planar InGaAs detector arrays were fabricated on NIN-InAs0.6P0.4/In0.8Ga0.2As/ InAs0.6P0.4 buf./InP materials by metal organic chemical vapor deposition (MOCVD). And the I-V characteristics, spectral response and detectivity of the detector at different temperatures were analyzed. The results indicate that the forward dark current is dominated by the generation-recombination current and gradually becomes the diffusion current with temperature dropping. Diffusion current and generation-recombination current were the main resource of reverse current of the detector between 260 K and 300 K. The tunneling current predominated at temperature below 180 K. The cutoff wavelength and peak wavelength were 2.57 μm and 2.09 μm at room temperature. The peak detectivity, peak responsivity and quantum efficiency was 7.25×108 cm·Hz1/2/W, 0.95 A/W and 56.9% respectively. Furthermore, the average peak detectivity of the detector arrays reached a peak value of 1.11×1011 cm·Hz1/2/W and the response nonuniformity was about 5.28% at 153 K.