Photodetectors

Abstract

Photodetectors, based on photon absorption or thermal emission, are made from semiconductor materials that are very sensitive in the spectral range from ultraviolet to far infrared. Detector figures of merit such as responsivity, noise, noise equivalent power and detectivity, and ideal performance and cooling requirements are given. Modes of operation include charge‐coupled device, photovoltaic diode, photoconductor, and bolometer. Most semiconductor detectors operate as photon detectors where the minimum photon energy detected is defined by a discrete activation energy of the semiconductor. However micromachined bolometers are in development for thermal imaging and chemical spectroscopy. Materials and detector types are discussed. Detector material preparation technologies are presented for intrinsic detectors where the photon absorption coefficient is high, and for the low absorption coefficient detectors such as impurity‐doped Ge or Si. Fabrication technology making possible large photodetector focal planes that detect photons and perform signal processing are integrated structures either in monolithic form or in hybrid form. The monolithic arrays range up to 10 6 detectors. The hybrid focal planes, mostly for infrared detection, contain up to 10 5 . Photodetector arrays have been developed for imaging across the spectrum and are used in CCD cameras, chemical spectroscopy, missile seekers, and night vision equipment.

Ultraviolet and Visible Spectroscopy

“…A possible arrangement of such a polychromator with a multiplex detector is shown in Figure 12. The resolution is determined by the specification of the grating and the number of diode elements in the array (256 -1024) [66].…”

Synthesis and characterization of thin films of P3HT − G/MoS2 nanocomposites in photodetectors applications

“…Photonic detector convert photons directly into free current carriers, when light falls on the detector the photons exciting the electrons to higher energy levels lead to forming electrical charge carriers (e or h) that remain inside the detector material. The incident photon must has energy equal or greater than band gap energy to excite valence electrons, the longest wavelength that can be absorbing is specific by cut-off wavelength (λ c ) given by the following equation: 27,28 E Q -T A R G E T ; t e m p : i n t r a l i n k -; e 0 0 1 ; 1 1 7 ; 4 9 9…”

“…Therefore, these reagents are preferred over thermal detectors because of their high detectivity, and response time is shorter than thermal reagents and does not require cooling. 27,28 It is an important parameter of the detector that was calculated.…”