A novel column-stage structure of readout integrated circuit (ROIC) for GaN ultraviolet (UV) focal plane array (FPA) working in “solar-blind” band is proposed. The column stage has better drive capability, higher dynamic range, stable bias current and low impedance. The noise voltage of the column readout stage is discussed, which has been reduced by small-current driving, column-stage sample and hold and the technology of divided-output-bus. This research on low-noise ROIC is designed for weak-current UV FPA. It is designed, simulated and laid out using the 0.35um 2P4M CMOS 5V process. The clock rate operates at 8MHz. The simulation input current sets 0.01nA. The output swing is 2.6V and power consumption is 40 mW according to the measurement results.
Noise pollution is often introduced during image data acquisition and transmission process. Oversampling technology
and algorithm used to improved moving average are applied to reduce noise in UV image project. Both theoretical
analysis and Matlab simulations results show that this technology is effective. Considering a virtual signal consisting of
Gaussian noise, the new algorithm make the signal’s mean square error (MSE) reduces from 0.01 to 0.0038, which are
better than traditional algorithm.
The ratio of optical pulse numbers to corona current (ROPC) is proposed to study the correlation between UV radiation
intensity and current strength during AC corona discharge. It’s found that the ROPC curves rose rapidly before a critical
voltage and then the curves flatten with the supplied voltage rising, even if the voltage is increased approximately 1 fold
higher than the critical voltage. Finally, according to ROPC curves, a new method of determining the voltage for corona
inception is introduced, and a novel quantitative analysis method is put forward to judge the level of corona discharge by the
means of optical measurement.
Two types of readout integrated circuit named SFD and CTIA are proposed to match the PVDF pyroelectric IR detector.
By employing macro model and analyzing the parameters of detector, the best matching conditions including the input
reference noise, input impedance, input capacitance, and working point are investigated in details. Based on the property
of the AC output for PVDF detector, we propose a novel readout method, with which the ratio of signal to noise can be
greatly improved. Furthermore, the linearity and sensitivity for both circuits are discussed by the means of Spectre tools.
Ozone layer intensively absorbs 240nm to 285 nm incidence, when the sunshine goes through stratospheric. There is
almost no UVC (200nm-280nm) band radiation existing below stratospheric. Because the radiation target presents a
strong contrast between atmosphere and background, solar-blind band radiation is very useful. Wide band gap materials,
especially III-V nitride materials, have attracted extensive interest. The direct band gap of GaN and A1N is 3.4 and 6.2
eV, respectively. Since they are miscible with each other and form a complete series of AlGaN alloys, AlGaN has direct
band gaps from 3.4 to 6.2 eV, corresponding to cutoff wavelengths from 365 to 200 nm. A back-illuminated hybrid FPA
has been developed by Shanghai Institute of Technical Physics Chinese Academy of Science. This paper reports the
performance of the 128x128 solar-blind AlGaN UV Focal Plane Arrays (FPAs). More and more a CTIA (capacitivetransimpedance)
readout circuit architecture has been proven to be well suited for AlGaN detectors arrays. The bared
readout circuit was first tested to find out optimal analog reference voltage. Second, this ROIC was tested in a standard
20-pin shielded dewar at 115 K to 330K. Then, a new test system was set up to obtain test UV FPA noise, swing voltage,
data valid time, operating speed, dynamic range, UV response etc. The results show that 128x128 back-illuminated
AlGaN PIN detector SNR is as high as 74db at the speed of above30 frame per second. Also, some noise test method is
mentioned.
The influence of larger constant current burning was studied and analyses on the failed detectors were given. "1/f" noise is observed in the reign of g-r noise, and the exponential factor had a trend of increasing with burning time. Peak wavelength and cutoff wavelength of the detectors had no apparent change during electrical burning, but there were decreases on the short wavelength side in spectral response. After a long time burning, minority carrier lifetime of the detectors decreased as well as black-body signals. Analyses showed that defects increased at the surface of detectors after burning, which was responsible for decreasing the detector performance, even detector failure.
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