Improvements in electrical properties, low frequency noise and detection performance of a Mn-based bilayer thin film infrared detector

Experimental studies about low frequency 1/f noise and detection performance of Mn-based monolayer and bilayer structured detectors produced by Radio Frequency (RF) sputtering method have been carried out. Mn1.56Co0.96Ni0.48O4 (MCN) thick film (10 μm) was deposited on sapphire substrate to produce infrared detector by using sacrificial layer techniques. An MCN thin film (1 μm) detector and an Mn1.56Co0.96Ni0.48O4-Mn1.56Co0.80Cu0.16Ni0.48O4 (MCN-MCCN) bilayer thin film detector were also constructed by using wet chemical etching methods. The XRD results exhibited that the three samples all showed spinel structures. The varied temperature characters of the MCN and bilayer film samples were examined by voltage-current measurements ranging 250-320 K, and the characteristic temperature values were derived from the R-T curve. All three detectors showed similar temperature coefficient of resistance at about −3.5%K−1 at 295 K. The low frequency noise spectra of all three detectors were all conducted, where the bilayer film detector showed half the noise value than that of the MCN thin film sample. The detector fabricated by the MCN-MCCN bilayer film showed large response to 1550 nm laser radiation, as well as good thermal sensing ability to a blackbody. It is found that the response speed of the bilayer detector is one order faster than the MCN thick film detectors, where the time constant is about 0.17 ms. The detectivity of the MCN-MCCN detector was estimated to be on the order of 107 cm∙Hz0. 5/W. Simple considerations on bias voltage and thermal conductance G are given for further improvements by using the thermal isolation structures.