Forward tunneling current in GaN-based blue light-emitting diodes

Forward tunneling current in InGaN/GaN multiquantum-well blue light-emitting diodes grown on sapphire substrate was studied by temperature-variable current-voltage (I-V) measurement. All semilog I-V curves obtained in the temperature range from 100 to 300 K exhibit two successive linearly dependent regions at low forward bias. The corresponding slopes appear to be insensitive to temperature, which indicates a dominant defect-assisted tunneling process. It is found that the tunneling current varies approximately as a function of ∼exp(−βEg+λeV), where β and λ are constants independent of temperature and voltage. The temperature- and voltage-dependence of forward tunneling current are explained by thermally induced band gap shrinkage and bias-induced route change of diagonal tunneling, respectively. The likely tunneling entities involved in the forward tunneling process are also discussed.