Observation and Modeling of Leakage Current in AlGaN Ultraviolet Light Emitting Diodes

Current-voltage ( I-V ) characteristics of AlGaN ultraviolet light-emitting diodes (UV-LEDs) under the temperatures ranging from 50 K to 300 K are analyzed. The abnormal diode characteristics of UV-LEDs below the turn-on voltage indicate the existence of space-charge-limited (SCL) current transport in the presence of deep trap states, which induce a non-linear current leakage effect. The SCL current is gradually overwhelmed by Ohmic leakage as the temperature increases, which is mainly due to the thermally generated carrier concentration and traps deactivation. A modified three-diode circuit model is suggested with an additional series resistor and diode to emulate the forward-bias I-V characteristics of UV-LEDs. An excellent fit to the I-V curves of UV-LEDs is achieved, which illustrates the impact of deep trap states on the electrical characteristics of UV-LEDs.