Nonlinear photoresponse of quantum well infrared photodetectors at high excitation power

摘要

Nonlinear photoresponse effects at high excitation power in Quantum Well Infrared Photodetectors (QWIPs) arc studied both experimentally and theoretically. The photoconductivity nonlinearity is mainly caused by a redistri¬bution of the electric potential at high power, which leads to a decrease of electric field in the bulk of the QWIP As a result of the decreased field, the photoexcited electron escape probability and drift velocity decrease, resulting in a decrease of responsivity. These effects are strongly influenced by QWIP structural parameters and operating conditions. In QWIPs with a few QWs the infrared power required to observe a decrease of responsivity is much lower than that needed to cause the saturation of the intersubband absorption. Key factors in designing a QWIP with a suppressed nonlinearity are discussed.