Optical detectors

In the context of More than Moore (MtM), an overview is given of optical detectors that are either commercially available today or in advanced development. Focus is placed on the integration in or with complementary metal-oxide-semiconductor (CMOS) technology that can provide electronic readout circuits as well as circuits for signal amplification and speed enhancement. Today, optical detectors form part of optical sensors used in a wide range of technologies spanning the electromagnetic spectrum from well below vacuum-ultraviolet wavelengths, through visual wavelengths to the <termDefinition xml:id="c11-tdef-0001">far infrared</termDefinition> ( <term definitionRef="#c11-tdef-0001" type="abbreviation" xml:id="c11-term-0001">FIR</term> ). Mobile telecommunication has particularly pushed the development of potent CMOS imagers comprised of Si photodiode (PD) pixels, suitable for visual to near-infrared wavelength detection, but many applications of the shorter ultraviolet wavelengths (e.g. monitoring/diagnostic systems in medicine, flame detection, radiation detection, and biosensors) and the longer infrared wavelengths (e.g. fiber optics, laser, remote sensing, data storage, and optical communication systems) are also under intensive development. The merging of CMOS electronics with <termDefinition xml:id="c11-tdef-0002">photonic integrated circuit</termDefinition> s ( <term definitionRef="#c11-tdef-0002" type="abbreviation" xml:id="c11-term-0002">PIC</term> s) is now being enabled by high-performance Ge-on-Si and InGaAs-based photodiodes. Wide-bandgap materials have been developed for solar-blind ultraviolet detectors. Narrow-bandgap photoconductors are suitable for infrared wavelengths up to about of 20 μm, beyond which thermal detectors are used. Alternative photodetector devices are being researched using special nanowire, quantum-well/-dot, and 2D-material structures that additionally may have their performance enhanced by adding plasmonic surface structures. These technologies aim to enhance the compatibility with CMOS by enabling direct integration at the chip level, either as front-end CMOS modules or as back-end add-ons.