The transient photocurrent response of a vertically stacked triple pn junction structure, which can detect three different colours simultaneously, is investigated. The triple pn junction structure is designed based on the effect that the penetration depth in silicon depends on light wavelength. To increase the bandwidth of optical sensor systems the transient photocurrent response is a critical parameter. The transient response is measured by applying three different light wavelengths to this triple junction structure. This triple pn junction structure is fabricated in a 0.6 µm BiCMOS technology using a p−p+ epitaxial wafer without any process modification. Based on the measurement results, it can be concluded that this triple pn junction structure can be applied to optical sensors without optical filters and the total data rate of this structure can reach up to 100 Mbit/s.
Within this work an integrated range finding single pixel sensor manufactured in a standard 90nm CMOS technology is presented. The sensor works on the time-of-flight principle obtaining the distance information out of the correlated sent and received signals. The implementation of a range-finding sensor in 90nm technology is using the most advanced process for a distance sensor up to now based on the bridge circuit. Background light suppression is inherently provided in the pixel sensor. The pixel facilitates a high fill factor accounting to 90% at an area of 50 × 64 µm² and has a power consumption of 2 µW. Measurement results show a standard deviation of 2 cm at 1.2 m covering the range from 0.2 to 3.2 m at 120 klx background illumination.
An analytical approach to model and analysis of the bit-error ratio (BER) performance in multi-single photon avalanche diode (SPAD) optical receivers is presented. The model covers all important non-ideality effects including the detector dead time, the optical signal profile, and the SPAD intrinsic parasitics. This is very helpful to understand the bottlenecks that limit the performance and, therefore, is critical to attempt further improvements. A good agreement to the experimental data is achieved and it is found that the crosstalk makes the major contribution to the BER as compared to the other parasitic effects including dark-counts and afterpulsing.
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