Hopping Transport of Charge Carriers in LEDs Based on Multiple InGaN/GaN Quantum Wells

The results of experimental studies of forward current-voltage characteristics of blue LEDs with an active region consisting of the multiple InGaN/GaN quantum wells are presented. A model explaining the limitation of the forward current at decreasing temperature is proposed. The model is based on the concept of current limited by the space charge and caused by hopping transport of electrons in the region of multiple quantum wells. It is shown that the most probable mechanism of charge accumulation is the electron capture by shallow traps. According to the results of different measurements, the activation energy of traps decreases with decreasing temperature, which is consistent with the concept of hopping conductance mechanism in materials with an exponential distribution of the defect state density in the band gap.