Long wavelength interband cascade infrared photodetectors operating at high temperatures

We report on a comparison study of long wavelength infrared interband cascade infrared photodetectors (ICIPs) with the goal of an improved understanding that will lead to further increases in the operation temperature. We studied four sets of detectors including single absorber barrier detectors and multi-stage ICIPs with four, six, and eight discrete absorbers. The 90% cutoff wavelength of these detectors was between 7.5 and 11.5 mu m from 78 to 340K. Multiple stage ICIPs were able to operate with monotonically increasing bias-independent responsivity up to 280K, while the responsivity of the one-stage detectors decreased at 200K with bias dependence. The advantages of the multi-stage ICIPs over the one-stage device are demonstrated in terms of lower dark current density, higher detectivity (D*), and higher operating temperatures. The one-stage detectors operated at temperatures up to 250K, while the ICIPs were able to operate up to 340K with D* higher than 1.0 x 10(8) cm . Hz(1/2)/W at 300K. The D* for these ICIPs at 200K was larger than 1.0 x 10(9) cm.Hz(1/2)/W at 8 mu m, which is more than a factor of two higher than the corresponding value for photovoltaic HgCdTe detectors at similar cutoff wavelengths. Interestingly, negative differential conductance (NDC) was observed in these detectors at high temperatures. The underlying physics of the NDC was investigated and correlated with the number of cascade stages and electron barriers. With the enhancement of the electron barrier in the multiple-stage ICIPs, the NDC was reduced, and the overall device performance, in terms of D*, was improved. Published by AIP Publishing.