Laurent Quiquerez

A time-integration based quenching circuit for Geiger-mode avalanche diodes

In this paper, a time-integration based passive quenching - active recharge circuit for Geiger-mode avalanche diodes has been proposed with the aim of minimizing the avalanche charge and providing a hold-off time tunable within wide range. These are indeed important features to be taken into account in the design of the avalanche diode quenching - reset electronics. Furthermore a hold-off time tunable within a wide range is typically desirable in every application where a full characterization of the device dark count rate is required. A correct operation of the proposed circuit, designed in a commercial High-Voltage CMOS 0.35um technology, is assessed through circuit simulations as well as Monte Carlo analysis in the Cadence Environment.

Noise Modeling For Charge Amplification and Sampling

A new cyclostationarity-based analytical model for noise analysis of a charge amplifier followed by a correlated double sampling (CDS) circuit is proposed. It determines output noise (power spectral density and squared voltage) resulting from input noise voltages and currents. Model validation is performed by comparing the obtained results with those of temporal noise simulations. This model allows analysis of consequences of CDS and integration duration on noise contributions. It predicts that CDS does not suppress or attenuate effect of input current sources. In the case of 1/f input noise current, the SNR can not be improved by increasing the integration duration.

A VHDL-AMS package for microsystems polychromatic optical modeling

For biomedical microanalysis systems requiring implementation of optical signal generation and detection, we propose a package of VHDL-AMS functions to allow co-simulations of optical path, opto-electronic elements and associated electronics. This package contains a set of functions, which may be used for functional description of parts of microanalysis systems. An overview of simulation techniques shows that VHDL-AMS allows continuous-time simulation of polychromatic optical signals needed by the wavelength shifting nature of fluorescence. Indeed, directivity of optic path is well managed by VHDL-AMS using directional ports. By design, optical signals are easily simulated together with associated command and processing electronic circuits. Inspired by RF simulation techniques, the proposed description of polychromatic optical signals lies on a discretization of spectra. This format allows each optic band to be processed independently by models. The array data structure available in VHDL-AMS provides a compact form to device descriptions and to optical signal connexions. Fluorescence is modelled with absorbance and emission spectra, and optical couplings are described using results of geometric-optic analysis. A “spectral plug-in” has been developed, to be connected to output-power models of LASER-LED reported in the literature. Furthermore, a physical model of the CMOS Buried Double Junction (BDJ) detector has been described. Models of optic and electronic parts include a modulated LASER source, fibre optic, fluorochrom, BDJ detector and Constant Voltage Threshold (CVT) analogue-to-digital signal conversion. The system-level simulations, with Variable-Time Synchronous Detection (VTSD) are performed using the “Advanced-MS” environment. The validity domain of this approach as well as limitations of the available VHDL-AMS simulators (especially in terms of convergence and simulation time) are discussed.

Design guidelines for the integration of Geiger-mode avalanche diodes in standard CMOS technologies

The goal of this paper is to provide some useful design guidelines at the device level regarding the main challenges to be typically faced in the design and integration of Geiger-mode avalanche diodes in a standard CMOS process. Different techniques are found in literature in order to avoid premature edge breakdown with the aim of limiting the electric field at the edges to be weaker than in the multiplication region. In this article, the use of such techniques, the conditions where they can effectively work and above all their limitations are studied by means of TCAD simulations for various diode architectures. Additionally, the noise performance is discussed by focusing on the band-to-band tunneling and shallow trench isolation enhanced dark count rates. Geiger-mode bias techniques as well as a synthesis on the pros and cons of the various avalanche diode architectures are finally presented aiming at facilitating future design choices.

Preliminary simulation study of a coincidence Avalanche Pixel Sensor

In this paper a preliminary study of coincidence Avalanche Pixel Sensors (APiX) for High Energy Physics (HEP) applications is presented. In this preliminary work, some PEB prevention techniques found in literature have been studied by TCAD simulations adopting 2D Cylindrical geometrical models and 130nm CMOS process technological data.

CMOS photodetection system with variable-time synchronous detection

For sensitive fluorescence detection requiring weak signal recovery, we propose a novel digital synchronous detection method. It is based on a voltage/time duality concept which, compared to a conventional approach, consists of transformation of constant sampling rate with voltage measurement into variable-time sampling with constant threshold voltage. This Variable-Time Synchronous Detection (VTSD) method ensures a constant SNR over a large dynamic range, with optimised measuring rate. It can be implemented without any precise analogue-to-digital converter. A CMOS photodetection system with implementation of this VTSD method together with charge amplification is designed and tested. The results confirm its ability to recover photocurrent signals at femto-Ampers levels.