**2. Experimental**

Experimental measurement in this paper was carried out on the commercially available photovoltaic detectors. In this experiment, the following were used:


Devices were first exposed to gamma radiation from Co60 source and then, after 30 days, to 241Am-Be neutron and gamma source. Both sources were housed in Institute of Nuclear Sciences "Vinča" in Belgrade, Serbia.

The dose of Co60 gamma source is 2000 Gy, the energy of 1.25 MeV, and half-life time of 5.27 years. The samples were placed in controlled environment at a distance of 150 mm away from the radioactive source with a glass between them. The dose rate was 100 Gy/hr which was measured by electrometer with ionization chamber TW 30012-0172 produced by PTW, Germany. Measurement uncertainty of the system is less than 1.2%.

241Am-Be source emits gamma photons of low energy (60 and 14 keV) with the activity of 3.7 × 1010 Bq, the intensity of the neutron emission of 2.7 × 106 neutrons s−1 and the mean energy of the neutrons *E*nav = 5.5 MeV. The panels were at a distance of 5 cm from the source, so the photon equivalent dose rate is *Ḣ*γ = 12 mSv/hr, and the photon absorbed dose rate is *Ḋ*γ = 12 mGy/hr. Calculated neutron absorbed dose rate is *Ḋ*n = 1.714 mGy/hr and the equivalent dose rate of neutrons is *Ḣ*n = 12 mSv/hr with the quality factor *Q*n = 7. In this experiment, the semiconductor devices were placed at a distance of 5 cm from the 241Am-Be source, and the exposure period was 16.75 hr. Since the total absorbed dose, for that distance, is *Ḋ*tot = 13.714 mGy/hr and the total equivalent dose is *Ḣ*tot = 24 mSv/hr, the total absorbed dose for material components is *D*tot = 229.71 mGy and the total equivalent dose is *H*tot = 402 mSv.

Both irradiation and those from Co60 gamma source and those from 241Am-Be source were performed in the air at a temperature of 21°C and relative humidity of 40–70%.

Before and after every step of irradiation spectral response and photocurrent have been measured. The measurement were performed on the photodiodes and phototransistors, in highly controlled conditions at room temperature, which have previously been removed from the irradiation room. Samples have been divided in two groups. First group was irradiated only with neutron radiation and the second one with successive gamma and neutron radiation.

For the first group, there have been performed three measurements of the photodiodes and phototransistors parameters:

**1.** first measurement: just before neutron irradiation,

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

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

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

Experimental measurement in this paper was carried out on the commercially available

**1.** four types of silicon PIN photodiodes (BP104, BPW41N, BPW34 all manufactured by

**2.** two types of silicon NPN phototransistors (BPW40 manufactured by Telefunken elec‐

Devices were first exposed to gamma radiation from Co60 source and then, after 30 days, to 241Am-Be neutron and gamma source. Both sources were housed in Institute of Nuclear

The dose of Co60 gamma source is 2000 Gy, the energy of 1.25 MeV, and half-life time of 5.27 years. The samples were placed in controlled environment at a distance of 150 mm away from the radioactive source with a glass between them. The dose rate was 100 Gy/hr which was measured by electrometer with ionization chamber TW 30012-0172 produced by PTW,

241Am-Be source emits gamma photons of low energy (60 and 14 keV) with the activity of 3.7 × 1010 Bq, the intensity of the neutron emission of 2.7 × 106 neutrons s−1 and the mean energy of the neutrons *E*nav = 5.5 MeV. The panels were at a distance of 5 cm from the source,

photovoltaic detectors. In this experiment, the following were used:

Germany. Measurement uncertainty of the system is less than 1.2%.

very large.

70 Radiation Effects in Materials

effect of neutron and gamma radiation.

Vishay, and SFH203FA by Osram),

tronic and LTR4206 by LITEON).

Sciences "Vinča" in Belgrade, Serbia.

gamma and neutron radiation).

**2. Experimental**


For the second group there have been performed five measurements of the photodiodes and phototransistors parameters:


In order to perform the long-term isothermal annealing i.e. to give detectors enough time to recovery, the third and fifth measurement have been undertaken 30 days after the irradiation. Because of that, the changes occurring in the samples of the second group after the first irradiation (gamma) can be considered as a permanent. Standard measurement equipment (the professional digital multimeter AMPROBE 33XR) was used for measurement. Combined measurement uncertainty for all measurements was less than 1.2% [1, 2].

In order to understand the state of the semiconductor crystal lattice after exposure to gamma radiation and before neutron irradiation, a Monte Carlo transfer simulation of gamma photons through the photodiode and phototransistor have been performed.
