We report the fabrication of GaN nanopillars and their laser action characteristics under optical pumping measurement.
The nanopillars were fabricated from a GaN epitaxial wafer by self-assembled Ni nanomasked etching, followed by
epitaxial regrowth to form crystalline facets on the etched nanopillars. The regrowth process is intended to reduce
surface defects created during ICP-RIE etching. The density of etched GaN nanopillars is about 8.5x108/cm2 and the
diameter and height of GaN nanopillars are about 250 nm and 650 nm, respectively. The as grown GaN nanopillars
exhibit a random distribution with hexagonal pillar geometry. The sample is optically excited by frequency tripled
Nd:YAG pulsed laser. The Gaussian waist of pumping spot is 1.8 um. At low pumping intensity, the emission has a
broad spontaneous emission spectrum with maximum at 363 nm. As pump intensity increases, a narrow peak at 363 nm
emerges quickly from the broad spontaneous emission back ground. The lasing action occurs at threshold pump power
density of 122 MW/cm2. The emission linewidth decreases with pumping power across threshold and reaches a lowest
value of about 0.38 nm above threshold. The excitation-power-dependent spectra show that the lasing wavelength has a
slight blue shift as pump power increases. We remark that this is due the band filling of the increasing excited carrier
density.
We demonstrate high efficiency blue light emitting diodes with defect passivation layers. The defect passivation layers
were formed by defect selective wet etching, SiO2 deposition, and chemical mechanical polishing process. The process
does not require photolithography patterning. The threading dislocation density of grown sample was reduced down to
~4×107 cm-2. The defect passivated epi-wafer is used to grow light emitting diode (LED) and the output power of the
fabricated chip is enhanced by 45% at 20 mA compared to a reference one without using defect passivation.
High efficiency GaN-based light-emitting diodes (LEDs) are demonstrated by a nanoscale epitaxial lateral
overgrowth (NELO) method on a SiO2 nanorod-array patterned sapphire substrate (NAPSS). The SiO2 NAPSS was
fabricated by a self-assembled Ni nano clusters and reactive ion etching. The average diameter and density of the formed
SiO2 nanorod-array was about 100 to 150 nm and 3 x 109 cm-2. The transmission electron microscopy images suggest
that the voids between SiO2 nanorods and the stacking faults introduced during the NELO of GaN can effectively
suppress the threading dislocation density. The output power and external quantum efficiency of the fabricated LED by
NELO method on NAPSS were enhanced by 52% and 56% respectively, compared to those of a conventional LED. The
improvements originated from both the enhanced light extraction assisted by the NAPSS, and the reduced dislocation
densities using the NELO method.
A three-pair AlGaN/GaN multiple quantum well (MQW) structure with superlattices (SLs) was grown on
c-plane sapphire using metal organic chemical vapor deposition (MOCVD) system. The AlGaN barrier and GaN
well of the MQW structure were grown by atomic layer deposition (ALD) and conventional growth,
respectively. The HRTEM and HRXRD results show the grown structure has shape interface between SLs
layers and QWs with good periodicity. The AFM and SEM data show smooth surface morphology with low
RMS value and low defect density. The CL measurements also indicate uniform luminescence pattern at room
temperature. The AlGaN/GaN MQW with AlN/GaN SLs structure grown by ALD could be used to improve the
surface morphology by effectively suppress the threading dislocation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.