In order to obtain low-noise InGaAs focal plane arrays, it is necessary to adopt high-quality InGaAs material with a low unintentionally doping concentration(u-InGaAs) to fabricate the detector. Zn diffusion with sealed-ampoule method on the lattice-matched InP/In_0.53Ga_0.47As hetero-structure with a u-InGaAs absorption layer was carried out. And the Scanning Capacitance Microscopy (SCM) technology were used to study Zn diffusion in these samples. The results show that the junction depth increases significantly with the increase of diffusion temperature and time. The diffusion interface of materials with a u-InGaAs absorption layer tends to change slowly compared with relatively high concentration materials (5×10¹⁶ cm^-3). According to the experimental results, the diffusion coefficient of Zn into InP under 530 ℃ is figured out, which is 1.27×10^-12cm²/s. The Microwave Photo Conductivity Decay method (μ-PCD) is used to extract the minority carrier lifetime of the InGaAs absorption layer. The measured minority carrier lifetime is 5.2 μs. Response distribution of devices with a u-InGaAs absorption layer at room temperature were studied by Laser Beam Induced Current technique (LBIC). The results show that the effective optically sensitive area increases significantly. The minority carrier diffusion length L_D is 63 μm by fitting the experimental data, which is consistent with the theoretical calculation. The dark current density of the device with a u-InGaAs absorption layer is 7.9 nA/cm² at room temperature, and the activation energy E_a is 0.66 eV. By fitting the dark current composition of the device, the minority carrier lifetime τ_p of the absorption layer of the device is about 5.11 μs, and the fitted minority carrier lifetime is consistent with the measured minority carrier lifetime.