LONG-TERM INSTABILITY OF LITHIUM-DRIFTED SILICON DETECTOR

Using 1150 nm infrared light, the change in the detector sensitivity w as studied. As a simple measure of the states of the detector sensitiv ity, the time derivative of the photocurrent is proposed. In terms of the derivative, the change is uniquely classified into two categories. Even after the detector is aged, the derivative does not remain const ant with respect to time and voltage. The physical mechanisms which ca use the change are discussed based on possible effects due to unstable surface states and the accumulation of an oxide layer.