Metal oxide/silicon heterostructures: New solutions for different optoelectronic applications

In this paper we report the success in fabricating FTO/Si surface-barrier photodiodes produced by spray pyrolysis deposition technique, under ambient conditions. Three types of photodetectors for low-voltage-bias operation were developed based on high-resistivity silicon: 1. X-Ray detectors with energy resolution of 16.5% at 661.5 keV (¹³⁷Cs source), consisting of surface-barrier PIN photodiode with an active area of 50 mm² operating at 5 V reverse bias, scintillator based on monocrystalline Bi₄Ge₃O₁₂ and preamplifier (noise of 250 e^- RMS.); 2. Fast-response surface-barrier FTO/n^--n⁺ silicon epitaxial photodiodes, operating at 10 V bias with rise times of 2 ns at λ = 0.85 μm; 3. Radiation-resistant drift epitaxial surface-barrier PIN photodiodes for unbiased operating conditions, with an exponential impurity distribution in a 8 μm thick epitaxial layer. A built-in electrical field due to the carrier concentration distribution in the epitaxial layer provides a considerable improvement in the `critical fluence' value (3×10¹⁴ cm^-2) for neutron irradiation.