Dark current characteristics of GaAs-based 2.6 µm InGaAs photodetectors on different types of InAlAs buffer layers

GaAs-based In_0.83Ga_0.17As photodetectors (PDs) with cut-off wavelengths up to 2.6 µm are demonstrated. The effects of continuously-graded or fixed-composition InAlAs buffers on the device performances are investigated. The dark current characteristics of the PDs at various temperatures are analysed in detail. The photocurrents are also measured at 300 K; the detectivity of the PDs is extracted. The two GaAs-based PDs with different buffer schemes show different temperature-dependent dark current behaviours. The around room temperature performances of the GaAs-based device on the fixed-composition buffer are not as good, but comparable to those of InP-based devices, revealing a promising candidate for the GaAs-based PDs and focal plane arrays for many low-end applications. (paper)