InAs/GaSb superlattice infrared detectors
We report on the development of high-performance InAs/GaSb superlattice (SL) infrared (IR) detectors for the mid-wave-length (MWIR, 3-5 µm) and long-wavelength (LWIR, 8-12 µm) transmission window of the atmosphere. With a re-fined process technology, we are now able to fabricate dual-color focal plane arrays for the MWIR that excel at a very low number of noisy pixels. In an effort to correlate dark current and noise data of a larger number of devices, we found that for the description of the behavior in the white noise part of the spectrum, both, in InAs/GaSb SL photodiodes for the MWIR and the LWIR McIntyre's well-known model for excess noise of avalanche photodiodes is, in general, much more suited than the commonly used shot noise model. The analysis of dark current contributions is a convenient method to identify limiting mechanisms and extract material parameters such as the minority carrier lifetime. We show that even in large area devices the contribution of the sidewall leakage path should not be ignored for this kind of investigation. Finally, we present our Al-free heterojunction device concept for reduced dark current.