The uncooled InGaAs-based infrared detector has received great interest in recent years for its application in optical-fiber communication and remote sensing. However, the improvement of device performance is hampered by the lack of feasible method to monitor its device process. The Microwave Photoconductivity Decay (μ-PCD) technique is a contactless and non-destructive technique of the recombination lifetime characterization and mapping and has found wide application in semiconductor research. In this paper, a double heterojunction p-i-n InP/In0.53Ga0.47As/InP mesa structure was fabricated by Ar+ ion etching and the μ-PCD technique was applied to characterize the electrical effects of ion etching on this structure. The results revealed that the built-in field in the p-n junction played a critical role in recombination of photo induced minority carriers which made the mesa structure identifiable but not identical with the lifetime mapping of the sample. The recombination lifetime in the mesa was dominated by the recombination process in the edge of the mesa. The lifetime in the etched region was also influenced by the built-in field and increased with the decrease of distance to the mesa area. And ion etching brought great nonuniformity to the photo active cells.