Combined Action of Fast Neutrons and Operational Factors on Reliability of Infrared LEDs

Аннотация

Light-emitting diodes (LEDs) operate under conditions of ionizing irradiation. The purpose of this work is to research the action of preliminary irradiation with fast neutrons on the reliability of LEDs. The objects of research are LEDs based on double AlGaAs heterostructures. The control of the forward-bias region of the current–voltage characteristic of the LED allows detecting the parallel-connected dislocations to the p–n junction of the LED. Moreover, it makes possible to determine the resistance of ohmic contacts. The LEDs have an s-shaped form of the current–voltage characteristic, which is due to the connection of dislocations parallel to the p–n junction of its active layer. Long-term operating conditions are simulated by accelerated step-by-step tests. Analysis of the current–voltage characteristic shape makes it possible to mark several distinctive areas that are defined by the electron injection level in the active region of the LED. The marked areas can be characterized by corresponding threshold currents. The threshold currents go up when the step number increase is accompanied by an increase in resistance of ohmic contacts during step-by-step tests and under irradiation with fast neutrons. Preliminary irradiation with fast neutrons leads to a shift in the threshold currents depending on the fluence of fast neutrons. Preliminary irradiation with fast neutrons with fluence in the region of radiation-stimulated reconstruction of the initial defect structure makes it possible to increase the resistance of ohmic contacts during operation and, therefore, to increase their reliability. Preliminary irradiation with fast neutrons in the region of only radiation defects leads to the accelerated increase in resistance of ohmic contacts during operation, which decreases their reliability. Preliminary irradiation with fast neutrons can be used in the manufacturing technology of LEDs with the purpose of increasing the reliability.