Optoelectronic Integrated Circuits (OEICs)

The integration of photosensitive devices like photodiodes or phototransistors enables the realization of optical receivers and the following signal processing on a single chip. Possible applications are fiber receiver, pickup units for optical storage systems, or sensors, e.g. distance measurement.

Photomicrograph of an optoelectronic integrated circuit

© Horst Zimmermann

Microphotograph of OEIC

To publication list

Integrated fiber optical receiver reducing the gap to the quantum limit [SCIENTFIC REP.2017]

Experimental results of a single-photon avalanche diode (SPAD) based optical fiber receiver integrated in 0.35 μm PIN-photodiode CMOS technology are presented. To cope with the parasitic effects of SPADs an array of four receivers is implemented. The SPADs consist of a multiplication zone and a separate thick absorption zone to achieve a high photon detection probability (PDP). In addition cascoded quenchers allow to use a quenching voltage of twice the usual supply voltage, i.e. 6.6 V instead of 3.3 V, in order to increase the PDP further. Measurements result in sensitivities of -55.7 dBm at a data rate of 50 Mbit/s and -51.6 dBm at 100 Mbit/s for a wavelength of 635 nm and a bit-error ratio of 2 x 10-3, which is sufficient to perform error correction. These sensitivities are better than those of linear-mode APD receivers integrated in the same CMOS technology. These results are a major advance towards direct detection optical receivers working close to the quantum limit.

Picture: Quadruple SPAD receiver with bondwires. Circuit blocks are highlighted.

© Horst Zimmermann

4-SPAD optical receiver

Integration of photodiodes/phototransistors

Linear Mode Avalanche Photodiode With 1-GHz Bandwidth Fabricated in 0.35μm CMOS [PTL 2014]

We present an avalanche photodiode (APD) with separate absorption and multiplication zone. The APD is fabricated in a 0.35μm CMOS process using an epitaxial wafer. Due to its thick detection zone, this concept offers a high dynamic quantum efficiency and thus a high resulting dynamic responsivity. Measurements using a 670nm laser source demonstrate a maximum responsivity of 1.8∗104 A/W at 5 nW and a maximum bandwidth of 1.02 GHz at 5 μW illumination power. A maximum responsivity bandwidth product of 269.7 GHz∗A/W was found at 35 V reverse bias voltage and 5 nW optical power.

Schematic: Cross section of a SPAD with n++ cathode, p-well multiplication region, p-epi absorption region and p-substrate anode.

© Horst Zimmermann

Cross section (not to scale)

Optical freespace communication

Optical Wireless Communication With Adaptive Focus and MEMS-Based Beam Steering [PTL 2013]

An optical wireless communication system for an operation with wavelengths detectable by silicon optoelectronic integrated circuits is described. We use direct modulated vertical cavity surface emitting lasers as a transmitter. The field of view of the laser beam is adjusted with an adaptive optical system and aligned with a micro-electro-mechanical system based mirror for beam steering. To receive the modulated laser beam, we develop a receiver chip in 0.35 μm BiCMOS technology. The experimental system shows a 3 Gb/s wireless transmission over a distance of 7 m with a bit-error rate <10-9 without cost intensive optical components and complex adjustment procedure.

Photomicrograph: Opto receiver with satellite diodes for positioning of a laser used for free space transmission.

© Horst Zimmermann

Microphotograph of receiver chip

Low noise optical receivers

11Gb/s Monolithically Integrated Silicon Optical Receiver for 850nm Wavelength [IEEE ISSCC 06]

Using a vertical pin photodiode with a diameter of 50μm this high-speed optical receiver reaches a maximum data rate of more than 11Gbps. This high data rate is only possible due to equalization of the photocurrent and a reverse voltage at the photodiode of 17V. The chip was produced in a modified 0.5μm BiCMOS technology.

Diagram: Bit error rate over average optical power with data transmission rates between 8Gbps and 11.5Gbps.

© Horst Zimmermann

Bit Error Rate vs. average optical power

Optical receiver front-end for multilevel Signaling [IEEE Electronics Lett. 09]

A front-end optical receiver in 0.6 mm BiCMOS technology is introduced to maintain equally spaced levels and constant output signal swing for multilevel signals at different input optical powers. The symbol error rate measurements for 4-PAM signals show a better sensitivity than with a conventional optical receiver. It is believed that this is the first time that complete performance characteristics for an optical receiver front-end designed especially for multilevel data transmission have been reported.

Eye-diagram for 4-PAM receiver

© Horst Zimmermann

Eye-diagram for 4-PAM signal

Low-cost receivers

A 2.5Gbps Silicon Receiver OEIC with Large-Diameter Photodiode [IEEE Electronics Lett. 2004]

A silicon receiver optoelectronic integrated circuit (OEIC) in a 0.6μm BiCMOS technology is realized. The OEIC achieves with a 300μm-diameter pin photodiode a sensitivity of –20.1dBm at a data rate of 2.5Gbps and at a pseudo random bit sequence (PRBS) of 231-1 with a bit error rate (BER) of 10-9.

Photograph of an opto receiver with a PIN photo diode of 300 micrometers diameter.

© Horst Zimmermann

Microphotograph of OEICs

Optical distance measurement

A 2×32 Range Finding Sensor Array with Pixel-Inherent Suppression of Ambient Light up to 120kLux [IEEE ISSCC 09]

A new time-of-flight-pixel circuit managing up to 120kLux of ambient light without using any optical filter or burst mode operation for optical signal-to-noise-ratio enhancement is presented. The challenging task is to suppress the huge DC-photocurrent due to ambient light that is decades larger in worst case than the contribution of modulated light. Subtraction within one integration period might be the most obvious approach to solve this problem by introducing the bridge-correlator concept.

3D plot: Measurement result of the line sensor (only the first row). The measured and actual distance in every pixel is visualized.

© Horst Zimmermann

Measurement result of line sensor (only first row)

Picture of the line sensor (1280µmx50565µm) and of a single pixel (158µmx109µm).

© Horst Zimmermann

Microphotograph of line sensor and single pixel

Nonlinear optical receivers

130dB DR Transimpedance Amplifier with Monotonic Logarithmic Compression & High-Current Monitor [IEEE ISSCC 08]

Picture of the non-linear opto receiver. Circuit blocks are highlighted.

© Horst Zimmermann

Microphotograph of TIAs

Bandwidth

250MHz (2pF @ input)

Input current noise

58nA (2pF @ input)

Input current overdrive

200mA

Input current range

130dB

Consumption

110mA (from 3.3V)

Chip area

1.57mm2

Technology

0.35µm SiGe BiCMOS

Applications

optical sensing, free space optics, etc.