1 research outputs found
Highly efficient transverse-electric-dominant ultraviolet-c emission employing GaN multiple quantum disks in AlN nanowires matrix
Heavy reliance on extensively studied AlGaN based light emitting diodes (LEDs) to replace environmentally hazardous
mercury based ultraviolet (UV) lamps is inevitable. However, external quantum efficiency (EQE) for AlGaN based deep
UV emitters remains poor. Dislocation induced nonradiative recombination centers and poor electron-hole wavefunction
overlap due to the large polarization field induced quantum confined stark effect (QCSE) in “Al” rich AlGaN are some of
the key factors responsible for poor EQE. In addition, the transverse electric polarized light is extremely suppressed in
“Al”-rich AlGaN quantum wells (QWs) because of the undesired crossing over among the light hole (LH), heavy hole
(HH) and crystal-field split-off (SH) states. Here, optical and structural integrities of dislocation-free ultrathin GaN
quantum disk (QDisk) (~ 1.2 nm) embedded in AlN barrier (~ 3 nm) grown employing plasma-assisted molecular beam
epitaxy (PAMBE) are investigated considering it as a novel nanostructure to realize highly efficient TE polarized deep UV
emitters. The structural and chemical integrities of thus grown QDisks are investigated by high angle annular dark field
scanning transmission electron microscopy (HAADF-STEM). We, particularly, emphasize the polarization dependent
photoluminescence (PL) study of the GaN Disks to accomplish almost purely TE polarized UV (~ 260 nm) light. In
addition, we observed significantly high internal quantum efficiency (IQE) of ~ 80 %, which is attributed to the enhanced
overlap of the electron-hole wavefunction in extremely quantum confined ultrathin GaN QDisks, thereby presenting GaN
QDisks embedded in AlN nanowires as a practical pathway towards the efficient deep UV emitters