The structure and ultraviolet electroluminescence of n-ZnO-SiO 2-ZnO nanocomposite/p-GaN heterojunction LED
Journal
ECS Transactions
Journal Volume
33
Journal Issue
2
Pages
267-275
Date Issued
2010
Author(s)
Abstract
Ultraviolet (UV) light-emitting diodes composed of n-ZnO:Al-SiO2-ZnO nanocomposite/p-GaN:Mg heterojunction were fabricated on the c-plane sapphire substrate. TEM images clearly reveals a dispersion of high crystalline ZnO nanoparticles in the amorphous SiO2 matrix with sizes about 3~10 nm. Analyses of the Zn distribution by means of EDX and HAADF show a strongly non-uniform distribution of Zn within the SiO2 matrix. The SiO2-ZnO nanocomposite layer accomplishes a role of the current blocking layer and also causes, by its low refractive index, the increase in the light extraction efficiency from n-ZnO. With a SiO2 layer, significant UV electroluminescence from n-ZnO was achieved at a low forward-bias current of 1.8 mA. Strong UV emission arising from impact ionization in GaN, ZnO, and GaN:Mg states was also observed at reverse breakdown bias.
Type
conference paper