The development of InGaAs mesa detectors were presented briefly, then in order to verify the feasibility of fabricating backilluminated detectors by mesa junction, 8×1 elements mesa InGaAs detector arrays were made based on dopedInGaAs absorbing layer in MBEgrown PIN InP/InGaAs/InP doubleheterostructure epitaxial materials, with the technics of mesamaking, passivation, growth of electrode, backside polishing and so on.IV curves, response spectra and the signal of the detector were measured at the frontilluminated or backilluminated condition. The results indicate that the signal is almost same at the frontilluminated and backilluminated condition. The mean peak detectivity is 4．1×1011cm·Hz1/2·W-1 at the frontilluminated condition while it is 4.0×1011cm·Hz1/2·W-1 at the backilluminated condition, but the response spectra of the detectors has better cutoff characteristic at the backilluminated condition.