Current-Noise-Power-Spectra for Amorphous Silicon Photodiode Sensors

Abstract

Pixelated imaging arrays consisting of hydrogenated amorphous silicon (a-Si:H) photodiode sensors and field effect transistors are under development for x-ray imaging. For such arrays it is important to quantify the sensor noise characteristics as these may, in some cases, limit the array performance for certain applications. The current-noise-power-spectra of ∼1 nm thick a- Si:H p-i-n sensors of various areas are presented. The power spectra were measured for different reverse bias voltages over a frequency range of ∼0.01 to 1.0 Hz. The power spectra revealed the noise to be composed primarily of flicker noise. The flicker noise showed a l/fbdependence where b ranged from ∼1.1 to 1.2. The magnitude of the flicker noise as a function of the sensor leakage current and the sensor area has been investigated and is presented.