Performance characteristics of pulsed phototransistor structures under various conditions

Measurements are made on linear and area arrays of phototransistors operating in the steady-state and pulsed (integration) modes of operation. Description of the experimental setup is given. A simplified analysis of the pulsed mode of operation is presented. The heart of the study is concerned with measuring parameters critical to pulsed mode performance. The effects of temperature, readout voltage level, integration time, and device configuration on sensor operation are depicted. Increased leakage with temperature is found to change the proportionality constant between output and integration time. Both the saturation level and the dark response show a direct dependence on readout voltage. Varying the frame time (i.e., the integration time) is shown to be equivalent to changing the aperture setting of the optical system used to focus images onto the sensor. The relation between the steady-state photocurrent and the pulsed mode output has been established and is in agreement with analyses of the integration mode. The effects of collector pulse amplitude and temperature were found to match the relations derived from an extended analysis. An integration rate is extrapolated from the data. Images produced by a mechanically scanned line sensor and an area array are shown.