**1. Introduction**

Science and technology that deals with photovoltaic semiconductor detectors is an area with an extremely rapid development in the last 20 years. The reasons for this are, on the one hand,

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practically countless possibilities of application of these detectors (optical communication systems, medical devices, military equipment, automatic control systems, various electronic devices), and, on the other hand, miniaturization of electronic components and development of these devices mass production allowed them to have relatively low cost and to be accessi‐ ble to the wide population. Particularly interesting applications of semiconductor photovolta‐ ic detectors are in military systems, medical devices and equipment, and cosmic systems. These are areas where the probability for photovoltaic detectors to be in increased radiation field is very large.

The area of photovoltaic detectors and radiation type which they can be exposed is very large. This work is limited to the observation of the PIN photodiodes and phototransistors and their behavior in terms of gamma and neutron radiation considering that with particle emission from the core, as a rule, there have been a simultaneous de-excitations descendant core by a discrete gamma-ray emission. Semiconductor devices, therefore, are exposed to summary effect of neutron and gamma radiation.

The aim of this paper is to explore the impact of increased gamma and neutron radiation on the PIN photodiodes and phototransistors and their output characteristics. Special attention was paid to the observation of semiconductor devices' behavior when they have been exposed to the field of gamma radiation and after that to the field of neutron radiation (successive gamma and neutron radiation).
