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

We fabricated and characterized ultraviolet (UV) light-emitting diodes (LEDs) composed of
n
-ZnO/SiO
₂
-ZnO nanocomposite/
p
-GaN heterostructures. Significant UV electroluminescence at 387 nm from the
n
-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
n
-ZnO layer and the effective function of the SiO
₂
-ZnO nanocomposite layer. The SiO
₂
-ZnO nanocomposite layer accomplishes the role of current blocking by forming the larger energy barrier for electron injection from
n
-ZnO into
p
-GaN and also contributes to, due to its low refractive index, higher light extraction efficiency from the
n
-ZnO layer.