Radiation defects in GaP, GaAsP, InGaN LEDs

The GaP, GaAsP, and InGaN LEDs can be successfully used as model objects for studying the effect of accelerated particles on charge transfer processes in objects with the p-n junction, radiative recombination, and radiation resistance. The GaP output LEDs doped with N (green) and Zn,O (red),GaA_S1-XP_X - orange orange (х = 0.45) and yellow (х = 0.85), InGaN (blue) and irradiated with electrons with Е = 2МеV, F = 10¹⁵orange (х = 0.45) and yellow (х = 0.85), InGaN (blue) and irradiated with electrons with Е = 2МеV, F = 10¹⁵ cm:-² have been studied. On the current-voltage characteristics (CVC) at low temperatures (90-77 К) in GaP and GaAsP LEDs, arise of negative differential resistance (NDR) of the S-type, in the case of GaP is N-type has been revealed. The arise of S-similarity in GaP diodes can be caused by the structural features of the C- band; the formation of the N-region is associated with tunneling transitions of carriers of the band-defect-band type. The detected area of NDR in the GaAsP solid solution is due to the presence of the GaP component. Electron irradiation leads to the increase in the DR of the LEDs under study and to a decrease in the reverse currents. A breakdown section arises on the CVC of GaP diodes at significant reverse voltages (U = 15÷20 V); as the sample temperature rises, it shifts to the region of lower voltages, indicating the predominance of the tunneling breakdown mechanism. The value of the coefficient of the imperfection of GaP LEDs within the currents of 10^-7÷10^-4is in the range of n = 1.6 ÷ 1.7 which indicates the predominance of the tunnel-recombination component of the full current. By controlling the voltage change depending on the annealing temperature (T_anneal) at a constant current through the GaP sample, the U(T_anneal) curve can be divided into stages 20 ÷ 100°С and 160 ÷ 300 °С. The emergence of the first stage can be interpreted as a process of decay of unstable defect formations localized near large-scale structural disturbances, such as dislocations or dislocation networks. Annealing in the range of 150 ÷ 350°С, where the diffuse fluxes VP and VGa coincide, is the main one in terms of the scale of restoration of the CVC of the irradiated samples. The temperature dependence of the bandgap of the GaAsP solid solution is well described by the Varshni equation for A^IIIBV semiconductor compounds has been shown. The irradiation of GaAsP LEDs leads to the expansion of the spectral lines due to the action of fields of structural defects of radiation origin and a decrease in the glow intensity has been revealed. Compared to GaP diodes GaAsP LEDs are radiation-resistant their average radiation damage coefficient of the lifetime is close to 1.2 · 10^-10 cm²S^-1 and for GaP is 8 · 10^-8 cm²S^-1. Irradiation of InGaN LEDs with quantum wells causes a monotonic decreasing in the radiation intensity as a result of interbarrier tunneling of current carriers. (author)