  Lateral physical effects in single quantum well infrared photodetectors
(SQWIPs) under non-uniform illumination over detector area are considered.
These effects are due mainly to the in-plane transport of the photoinduced
charge in the QW. The length of the lateral photocurrent spreading is
determined by the in-plane conductivity of the carriers in the QW and
characteristic time of the QW recharging, and can be as large as 10-10000 mkm.
Closed-form analytical expressions for SQWIP responsivity for modulated
infrared signal and modulation transfer function are obtained. Possible
techniques to suppress lateral photocurrent spreading are discussed.
