The effect of $\gamma$-radiation on the electrical and optical characteristics of InGаN/GаN leds

Background. Despite the fact that InGaN / GaN-based structures have firmly conquered the LED market, some issues remain unresolved about how the electrical and optical characteristics of LEDs based on them change under the influence of external factors: temperature, current, radiation, etc. Of greatest interest is the change in the radiation intensity of the structure under the influence of external factors, i.e. mechanism of emergence and evolution of nonradiative recombination channels. The purpose of this work is to study the effect of $\gamma$-radiation on the volt-ampere and ampere-brightness characteristics of structures with quantum wells based on InGaN / GaN.
Materials and methods. To achieve this goal, the volt-ampere and ampere-brightness characteristics of the structure based on InGaN / GaN were measured in the range of currents up to $30$ mA at room temperature and radiation doses of $0$-$0.4$ MRad. The measurements of the electrical and optical characteristics were carried out in one cycle; when registering the ampere-brightness characteristic, the output signal was the photocurrent of the reverse-biased photodiode. To analyze the obtained volt-ampere characteristics, a generalized recombination model was used, which makes it possible to describe the process of current transfer in a spatially disordered structure, when tunneling is one of the stages of the process.
Results. The volt-ampere characteristics of InGaN/GaN-based structures are analyzed at room temperature for $\gamma$-ray irradiation doses of $0$-$0.4$ MRad. A significant change in the volt-ampere characteristics under the action of irradiation in the voltage range up to $3.1$ V. A change in volt-ampere characteristics causes a change in the dependences of the differential slope index $\beta$ on voltage and $\frac{d\beta}{dU}=f(U)$. A change in the ampere-brightness characteristics is found, which is consistent with the modification of the electrical properties under the action of irradiation with $\gamma$-quanta.
Conclusions. In the voltage range at an irradiation dose of $0.2$ MRad, a region $I_r(U)\sim exp(\frac{eU}{2kT})$ is observed, which is associated with the decomposition of Mg-H complexes, and hydrogen deactivation of the detected recombination center. This hypothesis is confirmed by a change in the amplitude of the extremum on the dependence $\frac{d\beta}{dU}=f(U)$, which is used to determine the presence of recombination centers in the structure under study, and the behavior of the ampere-brightness characteristics with increasing sample irradiation dose.