Lecture

Electron Multiplying CCD: Principles and Applications

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Description

This lecture discusses the principles of single photon detection using Electron Multiplying Charge-Coupled Devices (EM-CCDs). It begins with an overview of avalanche photodiodes, explaining how primary electrons are accelerated by an electric field, leading to impact ionization and the generation of electron-hole pairs. The instructor highlights the self-sustaining nature of the avalanche process and the critical importance of the breakdown voltage, which is temperature-dependent. The lecture then introduces hybrid photodetectors that combine electron bombardment gain with avalanche gain. The discussion transitions to frame transfer CCDs, detailing the process of recording images and transferring them to a storage matrix. The instructor explains the concept of a gain register that enhances the voltage between CCD cells, facilitating avalanche amplification through impact ionization. The lecture concludes with an explanation of the unidirectional avalanche effect and the potential for significant total gain through multiple stages, emphasizing the capabilities of EM-CCDs in low-light imaging applications.

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Related concepts (32)

Photodetector

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or by various performance metrics, such as spectral response. Semiconductor-based photodetectors typically photo detector have a p–n junction that converts light photons into current. The absorbed photons make electron–hole pairs in the depletion region.

Charge-coupled device

A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a major technology used in digital imaging. In a CCD , pixels are represented by p-doped metal–oxide–semiconductor (MOS) capacitors.

Photodiode

A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons. The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The package may include lenses or optical filters. Devices designed for use specially as a photodiode use a PIN junction rather than a p–n junction, to increase the speed of response. Photodiodes usually have a slower response time as their surface area increases.

Electron ionization

Electron ionization (EI, formerly known as electron impact ionization and electron bombardment ionization) is an ionization method in which energetic electrons interact with solid or gas phase atoms or molecules to produce ions. EI was one of the first ionization techniques developed for mass spectrometry. However, this method is still a popular ionization technique. This technique is considered a hard (high fragmentation) ionization method, since it uses highly energetic electrons to produce ions.

Avalanche photodiode

An avalanche photodiode (APD) is a highly sensitive semiconductor photodiode detector that exploits the photoelectric effect to convert light into electricity. From a functional standpoint, they can be regarded as the semiconductor analog of photomultiplier tubes. The avalanche photodiode (APD) was invented by Japanese engineer Jun-ichi Nishizawa in 1952. However, study of avalanche breakdown, microplasma defects in silicon and germanium and the investigation of optical detection using p-n junctions predate this patent.

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