Degradation of electrical and optical characteristics of photodetectors in increased temperature conditions is one of the most important limitation factors for their application. Since most of the electrical processes in semiconductor devices depend, to some extent, on temperature, investigations carried out at temperatures higher than room temperature may reveal possible changes in the output characteristics of a device. Temperature dependence of the current-voltage characteristics could suggest a dominant current flow mechanism, and the values of the ideality factor (n) and n(T) dependence could also indicate the presence, location and type of impurities and defects. This is especially important when impurities, localized near dislocations in the material, have energy levels deep in the energy gap. Such localized energy states could act as traps or recombination centers for charge carriers, modulating output current and inducing current noise in photodetector devices. So-called extent current (fluctuations in the output current), indicates the presence of both generation-recombination and burst noise. Magnitudes of these fluctuations are directly connected to the ideality factor and temperature, so monitoring of the n(T) dependence could indicate the changes (degradation) in not only electrical but also in optical properties of the photodiodes.