Cooled InAs photodiodes for IR applications

InAs photodiodes were prepared by cadmium diffusion into substrates with n-type conductivity. Formation of compensated region with concentration of free carriers ~1015 cm-3 is proved from measurements of barrier capacitance and transport mechanisms. The trap-assisted tunneling current is calculated for InAs photodiodes for the fist time. In this paper we proposed a model of the trap-assisted tunneling current which is caused by nonuniform distribution of impurity atoms and native defects. The trap-assisted tunneling current is caused by small areas of the junction which are characterized by increased concentration of defects and may be associated with dislocations, periphery of the junction or impurity fluctuations. Diffused photodiodes have higher threshold parameters in comparison with commercially available ones. Also, they exhibit higher photosensitivity in the short wavelength region due to existence of the surface built-in electric field.