Resonant Tunneling Effects on the Double-Barrier Electron Blocking Layer of a Nitride Deep-UV Light-Emitting Diode

The multi-quantum-barrier electron blocking layer (EBL) is reported to significantly improve efficiency by nearly 3 times over a single barrier in deep-UV AlGaN light-emitting diodes to deal with electron leakage. The improvement is usually attributed to the enhanced effective barrier height, and this article aims to explore the benefits of the tunneling effect by calculating the tunneling currents of electrons and holes through an Al0.6Ga0.4N/AlyGa1-yN double-barrier EBL under external bias from opposite directions. The results show that the tunneling current for holes J(h) is several orders of magnitude higher than that of the electrons J(e) as the barriers are with Al mole fraction y greater than 0.75 and thickness larger than 2 nm, which promises effective hole injection by tunneling without much electron leakage. Tunneling mechanism works better in EBL with higher and thicker barriers because the tunneling coefficients of light hole drop much slower than electrons due to its small effective mass. A proper distance between the barriers is needed to avoid electron leakage while holes tunnel through the EBL. Built-in electric fields tilt the band to enlarge the peak-to-valley ratio. This work indicates that the tunneling effect substantially facilitates a multibarrier EBL to enhance carrier-injection efficiency.