Transcript Slide 1

starting substrates were undoped 5 mm thick GaN films grown
by hydride vapor phase epitaxy (HVPE) on c-plane sapphire.
60 nm thick SiOx film was then deposited on the GaN film
using an electron beam evaporator
1 mm thick Al film was deposited
anodization was then carried out to create porous
anodic alumina (PAA)
PAA template serves as a mask to transfer the pore pattern into the SiOx layer
GaN nucleates on PAA under conventional growth conditions BUT GaN
does not readily nucleate on silica --> thereby allowing for selective
growth only in regions of exposed substrate
PAA was pore widened from ~10 nm to 60 nm (see Fig 1a)
sample was subjected to reactive ion etching (SF6 and O2,
were gases used)
PAA was then removed with by immersing the sample in a
5 vol % H3PO4 solution at 50°C for 60 min (see Fig 1b)
the GaN nanorods were grown from the GaN substrate, through
the pores in the SiOx template
the growth was done using organometallic vapor phase epitaxy
(OMVPE)
the SiOx film was removed by immersing the sample in
a buffered oxide etch for 20 s
prismatic faceting along with a pyramidal cap formed during the selfterminated growth as the nanorod grew beyond the silica template
with increased growth time, the nanorod tip came out of the silica template
and started growing laterally (but still maintained the pointed tip morphology)
SUMMARY
demonstrated a new nonlithographic and catalyst-free
technique for controllably growing GaN nanorods in place
possible nanophotonics applications due to the highaspect-ratio form factor and the quantum confinement
SUMMARY
“The Heterogeneous Integration Research Group was recently funded by
the NSF to exploit the elastic strain relief in nanorod heterostructures in
extending the spectral range of (In,Ga)N LEDs from uv-blue-green toward
amber and red. Today’s (In,Ga)N LEDs are familiar as the green traffic
lights with the intense color and pixilated appearance. Bright blue
(In,Ga)N LEDs are also manufactured in high volume, and are widely
employed in cell phones. These blue LEDs combined with a yellow
phosphor are also used in the first generation of white LEDs. The Purdue
effort is focused on understanding the relationship between strain and InN
incorporation in “quantum disks” grown within (In,Ga)N nanorods, with the
ultimate aim of demonstrating emission of light across the full visible
spectrum from a single nanostructured heterostructure, without phosphor
downconversion. Graduate students Parijat Deb (MSE), Sangho Kim
(ECE) and HoGyoung Kim (Physics) are working together to investigate
the epitaxial growth of (In,Ga)N nanorod arrays using OMVPE and a
custom-built halide vapor phase epitaxy (HVPE) reactor.”
https://engineering.purdue.edu/MSE/Features/TheNextSolidStateRevolutionEnergy
Sands Group Website:
https://engineering.purdue.edu/MSE/Fac_Staff/Faculty/TURNER_LAB/index_html/