Modeling and characterization of high TCR, low noise Si/Si1-xGex multi-quantum well detector for uncooled microbolometers

Uncooled infrared focal plane arrays (IR FPAs) have seen unprecedented growth over the last decade and ubiquitously extending its application beyond the military realm into various diverse areas such as: surveillance, security and law enforcement, thermography (predictive maintenance, building inspection), industrial process control, automotive safety and medical imaging. The uncooled microbolometers are mainly used for imaging in long wave infrared spectral range (LWIR). In the recent years, the e orts made for the technical evolution of the microbolometer involves: pixel size reduction, new materials and designs to enhance the detection and integration capability. Currently, Vanadium oxide VOx together with a-Si based FPAs have the major share in the uncooled imaging market. Nevertheless, they o er limited performance in terms of the thermal sensitivity. Here we present, an epitaxially grown Si/Si1-xGex multi-quantum-well (MQW) detector as a potential candidate to improve the thermal sensitivity due to its inherent fringe bene t of ease of the bandgap tailoring by increasing the Ge content up to 50 %. It offers low flicker noise attributed to its single crystalline properties. The predictive technology computer-aided design (TCAD) tool has been used to obtain a priori estimate to design and develop Si/Si1-xGex MQW detector. A comprehensive predictive device model is developed to investigate the electrical characteristics of Si/Si1-xGex MQW, device design challenges and design trade-o s. The integrated self-consistent numerical modeling framework incorporates the number of interdependent design variables such as Ge content, active device areas, the doping pro les, the thickness and the periodicity of quantum wells. The model is employed to optimize Ge content and the doping pro le for the desired Figure-of merits specified in terms of the temperature coefficient of resistance (TCR) and dc resistance (R). The modeling results are validated with the experimental data and found consistent over a wide range of Ge content varied from 30% up to 50 %. The model predicts TCR can be raised up to 5.4%K-1 by incorporating 50% Ge content in MQW (experimentally verified) where the measured flicker noise constant k1=f of the detector is 5.8 10-13

Assessment of genetic diversity and genetic characterization of Nili Ravi buffalo breed utilizing microsatellite markers

Background: Livestock contribution to Pakistan’s GDP is 11.2% and it engages 8 million of rural families for their livelihood. Estimated population of buffalo is 40.00 million heads in Pakistan mostly consisting of low genetic worth population resulting in low productivity and pressure on natural resources. Assessment of genetic diversity and genetic characterization of indigenous livestock resources is an essential step towards conservation and to gauge effects of various breed improvement efforts on population genetics.Methods: In present study genetic diversity of Nili Ravi buffalo population was assessed. A total of 196 unrelated Nili Ravi buffaloes from Punjab, Pakistan were sampled in this study. Genomic DNA was extracted and subjected to amplification using FAO recommended 12 Short Tandem Repeats (STRs) microsatellite markers. Among 12 microsatellite loci, 11 were successfully amplified (TGLA227, BM2113, ETH10, SPS115, TGLA126, TGLA122, INRA23, BM1818, ETH3, ETH225 and BM1824) whereas microsatellite locus TGLA53 was not amplified. Amplicons were resolved by genetic analyzer instrument and gene mapper software. Allele count, frequencies, gene diversity, heterozygosity, polymorphic information content (PIC) and linkage disequilibrium values were calculated by using Microsatellite toolkit v3 and Power Marker version 3.25.Results: A total of 96 alleles were detected in 196 samples with average of 8.73 alleles per locus and range of 5 alleles (ETH 3) to 18 alleles (ETH 225) per locus. Gene diversity ranged from 0.198 (BM1824) to 0.841 (ETH225), observed heterozygosity values ranged from 0.081 (ETH10) to 0.831 (BM2113) and PIC values ranged from 0.191 (BM1824) to 0.825 (ETH225).Conclusion: This study which will serve as a baseline to understand genetic dynamics of Nili Ravi buffalo breed. Highly polymorphic nature of STR markers will help in understanding effects of various breed improvements efforts on genetic diversity of Nili Ravi breed in future studies.Keywords: Microsatellite; STR; Nili Ravi Buffalo; Genetic Characterization; Punja

Model, design, and fabrication of antenna coupled metal-insulator-metal diodes for IR sensing

There is increasing demand for devices operating at room temperature for IR sensing and imaging. Antenna coupled metal-insulator-metal (MIM) diodes are potential candidates in this field. The reasons are miniaturizing features and femtosecond operation of these devices: smaller sizes lead to more pixels in limited areas and quantum tunneling phenomenon leads to faster operation. In this work, it is aimed to design and develop a device that can act as IR detector at room temperature

Device characteristics of antenna-coupled metal-insulator-metal diodes (rectenna) using Al2O3, TiO2, and Cr2O3 as insulator layer for energy harvesting applications

Antenna-coupled metal-insulator-metal devices are most potent candidate for future energy harvesting devices. The reason for that they are ultra-high speed devices that can rectify the electromagnetic radiation at high frequencies. In addition to their speed, they are also small devices that can have more number of devices in unit area. In this work, it is aimed design and develop a device which can harvest and detect IR radiation

High dynamic range smart pixel architecture for infrared focal plane arrays

This paper focuses on achieving high dynamic range pixel by using multiple pre-amplifiers in the pixel. There are two input circuits which are optimized for different signal levels inside the pixels. A smart circuit mechanism, inside each pixel, decides the best input circuit according to the incoming light level. In short, an individual pixel has the ability to select the best input amplifier circuit that performs the best SNR for the incoming signal level. A prototype chip is designed in 0.18 um CMOS technology. Pixel can achieve minimum 8.6 e-input referred noise and 98.9 dB dynamic range. In room temperature, power consumption of 2.8 uW is measured for the pixel

A novel approach to noise shaping in digital pixels for infrared imagers using over-integration

Digital readout integrated circuits (DROICs) for small pitch infrared focal plane arrays (IR-FPAs) suffer from low in-pixel resolution owing to the limited pixel real estate. To this end, a new technique to improve the resolution of pulse frequency modulation (PFM) based pixels, using quantization charge noise shaping, is presented. Multiple integration operations are performed in a single frame and the quantization error from each integration phase is retained and effectively induced into the next integration phase. The result is a high pass noise transfer function (NTF) equivalent to what is obtained in a first order sigma delta modulator. Along with a theoretical analysis of the technique, a prototype based on a single pixel and a 2nd order decimation filter is developed to demonstrate the performance of the proposed technique. With an in-pixel circuitry generating 5 bits, a resolution of 11 bits (65 dB) is achieved with an over-integration ratio of 64. With a 100 Hz frame rate and 64 integration operations per frame, a readout noise of 1100e- is measured at full-well fill from the test pixel fabricated in a 90nm CMOS process

Digital pixel readout integrated circuit architectures for LWIR

This paper presents and discusses digital pixel readout integrated circuit architectures for long wavelength infrared (LWIR) in CMOS technology. Presented architectures are designed for scanning and staring arrays type detectors respectively. For scanning arrays, digital time delay integration (TDI) is implemented on 8 pixels with sampling rate up to 3 using CMOS 180nm technology. Input referred noise of ROIC is below 750 rms electron meanwhile power dissipation is appreciably under 30mW. ROIC design is optimized to perform at room as well as cryogenic temperatures. For staring type arrays, a digital pixel architecture relying on coarse quantization with pulse frequency modulation (PFM) and novel approach of extended integration is presented.. It can achieve extreme charge handling capacity of 2.04Ge(-) with 20 bit output resolution and power dissipation below 350 nW in CMOS 90nm technology. Efficient mechanism of measuring the time to estimate the remaining charge on integration capacitor in order to achieve low SNR has employed

Low-power LVDS for digital readout circuits

This paper presents a mixed-signal LVDS driver in 90 nm CMOS technology. The designed LVDS core is to be used as a data link between Infrared Focal Plane Array (IRFPA) detector end and microprocessor input. Parallel data from 220 pixels of IRFPA is serialized by LVDS driver and read out to microprocessor. It also offers a reduced power consumption rate, high data transmission speed and utilizes dense placement of devices for area efficiency. The entire output driver circuit including input buffer draws 5mA while the output swing is 500mV at power supply of 1.2V for data rate of 6.4Gbps. Total LVDS chip area is 0.79 mm(2). Due to these features, the designed LVDS driver is suitable for purposes such as portable, high-speed imaging

Cryogenic measurements of a digital pixel readout integrated circuit for LWIR

This paper presents and discusses the cryogenic temperature (77K) measurement results of a digital readout integrated circuit (DROIC) for a 32x32 long wavelength infrared pixel sensor array designed in 90nm CMOS process. The chip achieves a signal-to-noise ratio (SNR) of 58dB with a charge handling capacity of 2.03Ge- at cryogenic temperature with 1.3mW of power dissipation. The performance of the readout is discussed in terms of power dissipation, charge handling capacity and SNR considering the fact that the process library models are not optimized for cryogenic temperature operation of the Metal-Oxide-Semiconductor (MOS) devices. These results provide an insight to foresee the design confrontations due to non-optimized device models for cryogenic temperatures particularly for short channel devices

A PFM based digital pixel with off-pixel residue measurement for 15 mu m pitch MWIR FPAs

Digital pixels based on pulse frequency modulation (PFM) employ counting techniques to achieve very high charge handling capability compared to their analog counterparts. Moreover, extended counting methods making use of leftover charge (residue) on the integration capacitor help improve the noise performance of these pixels. However, medium wave infrared (MWIR) focal plane arrays (FPAs) having smaller pixel pitch are constrained in terms of pixel area which makes it difficult to add extended counting circuitry to the pixel. Thus, this paper investigates the performance of digital pixels employing off-pixel residue measurement. A circuit prototype of such a pixel has been designed for 15 mu m pixel pitch and fabricated in 90nm CMOS. The prototype is composed of a pixel front-end based on a PFM loop. The front-end is a modified version of conventional design providing a means for buffering the signal that needs to be converted to a digital value by an off-pixel ADC. The pixel has an integration phase and a residue measurement phase. Measured integration performance of the pixel has been reported in this paper for various detector currents and integration times