Structure and Ultraviolet Electroluminescence of $n \hbox{-ZnO/SiO}_{2}\hbox{-ZnO}$ Nanocomposite/$p$ -GaN Heterostructure Light-Emitting Diodes

Abstract

We fabricated and characterized ultraviolet (UV) light-emitting diodes (LEDs) composed of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -ZnO/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZnO nanocomposite/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN heterostructures. Significant UV electroluminescence at 387 nm from the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -ZnO layer in this heterostructure LED was observed at a forward-bias current of as low as 1.8 mA. This is ascribed to the high quality of the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -ZnO layer and the effective function of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZnO nanocomposite layer. The SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -ZnO nanocomposite layer accomplishes the role of current blocking by forming the larger energy barrier for electron injection from <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -ZnO into <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN and also contributes to, due to its low refractive index, higher light extraction efficiency from the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -ZnO layer.