Study On Low-input-offset ROIC For Extended Wavelength InGaAs Infrared Focal Plane Arrays

Extended-wavelength In Ga As infrared focal plane arrays(IRFPA) have wide applications in the fields of aerospace, military and commercial. Because of the lattice mismatch, the dark current of extended-wavelength In Ga As sensor with 2.5μm cutoff wavelength is several orders of magnitude higher than In Ga As sensor with 1.7μm cutoff wavelength. Thus, decreasing the dark current of extended-wavelength In Ga As sensors is a problem to be solved. On the one hand, the dark current can be reduced by optimizing the materials and processes of devices. On the other hand, as the dark current of sensor has close relationship with the bias voltage, it also can be decreased by reducing the bias voltage of the sensor.This paper aims to research the readout circuit(RIOC) of IRFPA and designs low bias input stage. Firstly, the present situation and development of extended-wavelength In Ga As IRFPA is introduced. Several kinds of input stage of ROIC are discussed and research and comparison are made in structures with dark current suppression function. In the third chapter, the relationship between offset voltage and the sizes of MOSFETs in an op-amp is analyzed and simulated with Monte Carlo method. A new input stage structure of small-pitch IRFPA is discussed. In the fourth chapter, a new CTIA structure with autozero is discussed. A CMOS inverter with double power supply is introduced in the negative feedback circuit to eliminate the influence of leakage current of switch. The result of simulation implies that the offset voltage is reduced to 23μV.According to the testing results, the dark current of InGaAs sensors with 1.7μm cutoff wavelength is reduced to 10 f A magnitude after interconnection with ROIC chip, which is an order of magnitude lower than the test value at 10 m V reverse bias voltage. After interconnection with 2.5μm cutoff wavelength infrared sensors, the dark current is an order of magnitude lower than the test value at 10 m V reverse bias voltage at the temperature of 180 K, 200 K, 220 K and 240 K.