Low-frequency noise and reliability of infrared detectors based on ternary Mn-Ni-Co

Degradation of low-frequency noise (LFN) of infrared detectors (IR), based on thin film thermistors of ternary Mn-Ni-Co-O, is one of their main failure modes. Three kinds of stresses, short-term isothermal ageing (40°C, hold for 4 hours), long-term isothermal ageing with bias (bias voltage of ±15V, 40°C, hold for 600 hours) and thermal cycling (-40°C to +40°C, 1°C/min, hold for one hour, 20 cyclings), induced degradations in IR have been investigated. The results show that the ageing characteristics of electrical resistance of the samples with the same chemical composition and technological parameters may have the similar behaviour; however, the degradation of LFN shows different trends, and all malfunctions present abrupt increment of LFN. The changes of the noise figure of the samples under three stresses assume that there are two sources of LFN, namely, the contact noise at the solder joints which used to bound the inner Pt leads, and the thermistor bulk noise. The degradations of LFN during the short-term isothermal ageing and long-term isothermal ageing with dc bias may be ascribed to the defects within the thermistor bulk; these two degradations show positive correlation. The degradations of LFN during the thermal cycling may be ascribed to the defects at the contacts. Thus, analyzing the short-term isothermal ageing and thermal cycling induced degradations of the LFN of IR could be an effective screening method, which can significantly shorten the test time.