Optional CMOS based Monolithic Light Sensor for Detection of Light Intensity

Conventional light intensity sensing devices such as a light meter are big in size and incapable of outputting a digitized signal to a microprocessor for further control and actuation. Sensor transducers based on CMOS has therefore increased in popularity. Using CMOS technology, manufacturing costs and the power consumption can be reduced with smaller form factor. This paper presents a proposed design of light sensor for the detection of light intensity. The project utilizes Silterra’s 130 nm CMOS architecture to create a low power and low space monolithic light sensor chip that is able to detect the intensity of light to assist in achieving the recommended levels of light intensity in domestic areas. The light intensity was simulated with a photocurrent and the photodiode operates optimally at a wavelength of 555 nm, the spectral sensitivity of the human eye and has good linearity. The light intensity detected is shown in illuminance (lux) and this project is capable to detect illuminance in the range of 0 to 200 lux with a resolution of 20 lux. The monolithic chip of the light intensity sensor comprises of the transimpedance amplifier which acts as a current to voltage converter and an ADC to convert the analog voltage into a digital reading.  Hence, the output of the light intensity sensor is in binary representation.  The total power consumption of the monolithic light intensity sensor is 1.88mW and the total size of the design is 0.01202 mm2

Monolithic Perimeter Gated Single Photon Avalanche Diode Based Optical Detector in Standard CMOS

Since the 1930\u27s photomultiplier tubes (PMTs) have been used in single photon detection. Single photon avalanche diodes (SPADs) are p-n junctions operated in the Geiger mode. Unlike PMTs, CMOS based SPADs are smaller in size, insensitive to magnetic fields, less expensive, less temperature dependent, and have lower bias voltages. Using appropriate readout circuitry, they measure properties of single photons, such as energy, arrival time, and spatial path making them excellent candidates for single photon detection. CMOS SPADs suffer from premature breakdown due to the non-uniform distribution of the electric field. This prevents full volumetric breakdown of the device and reduces the detection effciency by increasing the noise. A novel device known as the perimeter gated SPAD (PGSPAD) is adopted in this dissertation for mitigating the premature perimeter breakdown without compromising the fill-factor of the device. The novel contributions of this work are as follows. A novel simulation model, including SPICE characteristics and the stochastic behavior, has been developed for the perimeter gated SPAD. This model has the ability to simulate the static current-voltage and dynamic response characteristics. It also simulates the noise and spectral response. A perimeter gated silicon photomultiplier, with improved signal to noise ratio, is reported for the first time. The gate voltage reduces the dark current of the silicon photomultiplier by preventing the premature breakdown. A digital SPAD with the tunable dynamic range and sensitivity is demonstrated for the first time. This pixel can be used for weak optical signal application when relatively higher sensitivity and lower input dynamic range is required. By making the sensitivity-dynamic range trade-off the same detector can be used for applications with relatively higher optical power. Finally, an array has been developed using the digital silicon photomultiplier in which the dead time of the pixels have been reduced. This digital photomultiplier features noise variation compensation between the pixels