1/f Noise QWIPs, Superlattice, and nBn Detectors

The low-frequency noise is a ubiquitous phenomenon and the spectral power density of this fluctuation process is inversely proportional to the frequency of the signal. We have measured the 1/f noise of a 640x512 pixel quantum well infrared photodetector (QWIP) focal plane array (FPA) with 6.2 microns peak wavelength. Our experimental observations show that this QWIP FPA’s 1/f noise corner frequency is about 0.1 mHz. With this kind of low frequency stability, QWIPs could unveil a new class of infrared applications that have never been imagined before. Additionally, we investigated the noise and gain of high-performance long-wavelength superlattice infrared photodetectors. We directly measured the noise spectra of a high performance superlattice detector, and shown that 1/ f noise is not intrinsically present in these structures. However, we found that a very large extraneous frequency-dependent noise can be generated by side-wall leakage currents. Analysis of the noise and gain indicate that the exact dependence of the shot noise on the dark current in these superlattice heterodiodes can be different from that in the diffusion-limited diode homojunction. Furthermore, we present the results from a similar 1/f noise measurement of bulk InAsSb absorber (lattice matched to GaSb substrate) nBn detector array with 4.0 microns cutoff wavelength.