Photoconductor Gain: Noise and Optimization Techniques

This lecture discusses the principles of infrared photodetectors, focusing on the gain and noise characteristics of photoconductors. It begins with the influence of minority traps on carrier dynamics, explaining how trapping minority carriers helps maintain neutrality. The instructor elaborates on the relationship between the lifetime of minority carriers and the transit time of majority carriers, which is crucial for understanding photoconductor gain. The lecture also covers the trade-offs in response time and bandwidth, emphasizing the need to reduce drift time for improved performance. Various optimization strategies for photoconductor structures are presented, including the selection of semiconductor materials and the introduction of traps to enhance carrier lifetime. The measurement circuits used to analyze photoconductors are illustrated, along with examples of structures and their characteristics. The discussion extends to noise sources in photoconductors, including 1/f noise and thermal noise, and the importance of working frequency in noise measurement. The lecture concludes with insights into the quantum nature of photoconductivity and its implications for device performance.