The Transport Mechanisms of Reverse Leakage Current in Ultraviolet Light-Emitting Diodes**Supported by the National Natural Science Foundation of China under Grant Nos 61334002, 61474091, 61404097, 61574110 and 61574112, the 111 Project of China under Grant No B12026, and the Scientific Research Foundation for the Returned Overseas Chinese Scholars of State Education Ministry of China under Grant No JY0600132501.

Abstract

The transport mechanisms of the reverse leakage current in the UV light-emitting diodes (380 nm) are investigated by the temperature-dependent current-voltage measurement first. Three possible transport mechanisms, the space-limited-charge conduction, the variable-range hopping and the Poole—Frenkel emission, are proposed to explain the transport process of the reverse leakage current above 295 K, respectively. With the in-depth investigation, the former two transport mechanisms are excluded. It is found that the experimental data agree well with the Poole—Frenkel emission model. Furthermore, the activation energies of the traps that cause the reverse leakage current are extracted, which are 0.05 eV, 0.09 eV, and 0.11 eV, respectively. This indicates that at least three types of trap states are located below the bottom of the conduction band in the depletion region of the UV LEDs.