Infrared Photodetectors: MSM and Photoconductors Overview

This lecture discusses infrared photodetectors, focusing on metal semiconductor metal (MSM) detectors and photoconductors. It begins with a review of thermal detectors for mid-infrared wavelengths, highlighting their limitations and the need for cooling. The instructor explains the requirements for effective photonic detectors, emphasizing the necessity of using semiconductors with small energy gaps. The lecture details the structure and operation of MSM detectors, including the role of Schottky junctions and the impact of bias voltage on performance. Advantages such as simplicity and speed are noted, alongside disadvantages like large dark currents and the need for cooling. The discussion then shifts to photoconductors, explaining their operation under illumination and the significance of minimizing doping to reduce dark current. The concept of internal gain in photoconductors is introduced, illustrating how it allows for enhanced performance. The lecture concludes with a preview of further exploration into internal gain mechanisms in subsequent discussions.