Need guidance for preamplifier fibre optic dosimetry

I am making tranimpedence amplifier by using IC op27G and photo diode s1223-1 and i could only detect 0.7 uA signal via Rf 1.0 M and if i increases Rf value then getting noise. As I want to detect pA order current... could you please suggest/guide for better selection of ic and photodiode...