Low Temperature Properties of Organic-Inorganic Ag / p-CuPc/ n-GaAs / Ag Photoelectric Sensor

A thin organic film of p-type semiconducting copper phthalocynanine (CuPc) was deposited by vacuum evaporation on an n-type GaAs single-crystal semiconductor substrate. The fabricated Ag/CuPc/n-GaAs/Ag sensor was carried through an ageing process to stabilize the parameters. Voltage-current characteristics and photoelectrical response of the sensor were investigated at a wide temperature interval of 82 K to 350 K. Photoelectric characteristics were measured under nonmodulated filament-lamp illumination. It was observed that sensor parameters such as: rectification ratio; threshold voltage; junction, shunt and series resistances; open-circuit voltage and short circuit current are temperature dependent. It was found that wide-range voltage-current characteristics of the sensor may be described similar to that of a Schottky barrier diode. Using the experimental data on voltage-current characteristics and absorbance of the CuPc films the energy-band diagram of the p-CuPc/n-GaAs heterojunction was developed. It was shown that data obtained from simulation of an equivalent circuit of photoelectric sensor agreed with experimental results.