Improvement in Electrical and Optical Performances of GaN-Based LED With $\hbox{SiO}_{2}/\hbox{Al}_{2}\hbox{O}_{3}$ Double Dielectric Stack Layer

A
$\hbox{SiO}_{2}/\hbox{Al}_{2}\hbox{O}_{3}$
double dielectric stack layer was deposited on the surface of a GaN-based light-emitting diode (LED). The double dielectric stack layer increases the optical output power of the LED because the first
$ \hbox{Al}_{2}\hbox{O}_{3}$
layer plays a role as an effective surface passivation layer and the second
$\hbox{SiO}_{2}$
layer with lower index increases the critical angle of the emitted light and hence the overall extraction efficiency from the LED. The leakage current of the LED passivated with an
$\hbox{Al}_{2}\hbox{O}_{3}$
layer was
$-\hbox{3.46} \times \hbox{10}^{-11}\ \hbox{A}$
at
$-$
5 V, at least two and three orders lower in magnitude compared to that passivated with a
$\hbox{SiO}_{2}$
layer
$(-\hbox{7.14} \times \hbox{10}^{-9}\ \hbox{A})$
and that of the nonpassivated LED
$(-\hbox{1.9} \times \hbox{10}^{-8}\ \hbox{A})$
, respectively, which indicates that the
$\hbox{Al}_{2}\hbox{O}_{3}$
layer is very effective in passivating the exposed GaN surface after dry etching and hence reduces the nonradiative recombination as well as reabsorption of the emitted light near the etched surface.