Read-out characteristics of the PbS-Si HJ detector

The read-out characteristics of the PbS-Si HJD are presented. An n-channel MOSFET structure fabricated within a p-well formed on an n-type Si substrate has been used to simulate the integrated device. The gmof the MOSFET was measured in the subthreshold regime and was found to follow the relation gm= qIo^2/3/nkT over the range 10^-5to 10^-8A. The PbS-Si HJD was connected to the read-out MOSFET in the source-coupled, direct injection mode. The read-out operation was characterized as a function of photosignal intensity and detector bias current. The injection efficiency of the read-out was determined from the nINJ= I´ph/Iphratio, where I´phis the photocurrent measured with the direct injection read-out and Iphis the photocurrent measured with a virtual ground transimpedance preamplifier. Good agreement between the experimental and theoretical injection efficiency has been found over a wide range. We have measured injection efficiencies as high as 90%.