HgCdTe epitaxial materials are grown on CdZnTe substrates by an Isothermal Vapor Phase Epitaxy (ISOVPE) method. On this base, a HgCdTe photovoltaic detector with an integrated optically immersed lens structure operating in the waveband from 2.5 μm to 3.2 μm at near room temperature is developed. Because the HgCdTe epitaxial material grown by ISOVPE has a greater composition gradient, its cutoff wavelength is located accurately by a method in which wet etching and transmission spectral measurement are carried out for many times. An integrated optically immersed lens with a diameter of 1.5 mm is made on a CdZnTe substrate by a single point diamond turning method. Then, the optical response area of the device before and after the integrated optically immersed lens is made is evaluated by a Laser Beam Induced Current (LBIC) test method. By comparing the current voltage characteristic curves of the device before and after the integrated optically immersed lens is made, the processing of the lens is evaluated. It is found that the zero biased resistance of the device increases slightly after the lens is made,which coincides with the fact that a hyper-semispherical structure may reduce the incident angle of radiation for the device. The blackbody signal and noise of the device are measured before and after the lens is made. The result shows that the signal of the device with an integrated optically immersed lens is increased by a factor of 20 to 30 and its noise is reduced slightly due to the increase of zero biased resistance.