Abstract: One challenge for the realization of electrically drive nano-photonic devices is the
formation of metal contacts and passivation. In this paper, we report a novel self-aligned method
suitable for the formation of the metal contact and passivation for submicron photonic devices. Two
different dielectric materials with high selectivity in wet chemical etching and a wet etching of
semiconductor to create an undercut are involved. The whole process is completely compatible with
existing compound semiconductor process. As a demonstration of this method, the fabrication and
characterization of an InGaAsP/InP submicron-ridge waveguide lasers is presented. The method is
extendable to high aspect ratio-submicron ridge waveguide and other device fabrication.
Abstract: We investigate the influence of sputtered silica as annealing cap on the enhancement of
intermixing rate of semiconductor quantum nanostructures. After sputtered silica application and
subsequent rapid thermal annealing, we observed bandgap shift of over 200 meV with respect to the
bandgap of as-grown material from various GaAs-based quantum well (QW) heterostructures such
as GaAs/AlGaAs, InAlGaP/GaAs, and GaAs/AlGaAs systems at significantly lower temperature
than the conventional dielectric cap process with plasma enhanced chemical vapor deposition
(PECVD). The results suggest that the sputtered silica process is a promising intermixing technique
for the monolithic integration of multiple active/passive photonic components on GaAs-based
Abstract: In this paper, we present the theoretical investigation of index-coupled distributed
feedback (DFB) laser with tilted single mode ridge waveguides. By tilting part of the ridge
waveguide in various degrees, DFB laser with manifold effective grating periods can be realized.
The structure is analyzed using couple mode theory in matrix form based on threshold analysis.
Important parameters of DFB laser like resonant frequency and threshold gains are obtained by
solving the eigen-equation. The results indicate not only that the lasing frequency is modulated by
the waveguide titling angle, but also large Gain Margin (GM) can be achieved at the threshold
condition which enhance the stable single mode operation in index-coupled DFB laser.
Abstract: This paper presents the structural and optical studies of porous GaN sample compared to
the corresponding as grown GaN. The samples were investigated by scanning electron microscopy
(SEM), high resolution x-ray diffraction (HRXRD), and photoluminescence (PL). The porous area
is very uniform, with pore diameter in the range of 80-110 nm. XRD measurements showed that the
(0002) diffraction plane peak width of porous samples was slightly broader than the as-grown
sample. PL measurements revealed that the near band edge peak of the porous samples were redshifted.
Metal-semiconductor-metal (MSM) photodiode was fabricated on the samples. For as
grown GaN sample, this detector shows a sharp cut-off wavelength at 362 nm. A maximum
responsivity of 0.258 A/W was achieved at 360 nm. For the porous GaN sample, this detector
shows a sharp cut-off wavelength at 364 nm. A maximum responsivity of 0.771 A/W was achieved
at 363 nm.
Abstract: We report on the growth mechanism, structural and optical characterstics of
Gallium nitride nanowires prepared on sapphire substrates (0001) by reacting metal
gallium with Gallium nitride powder and ammonia in the temperature range of 800 to
1050°C. GaN nanowires samples were characterized by using X-ray diffraction technique
which shows wurtzite structure of GaN nanowires and the lattice parameters are
calculated. Scanning electron microscopy images reveals that the dimension of the
nanowires are around 60 – 80 nm and the length of 1 - 2 millimeters. Three Raman
modes of GaN have been observed at frequencies 530, 554 and 564 cm-1.
Photoluminescence spectrum reveals the band edge at 3.4 eV and gives yellow
Abstract: In a hybrid discrete-continuum description the optical response of a capped monolayer of
nano-objects has been determined. The monolayer emits a summation of partial plane waves
obeying traditional reflection and transmission, enabling solution of the monolayer dipole strength.
For thick capping layers the resulting reflection coefficients could be approximated by analytical
expressions. These results have been used to investigate the feasibility of experimental detection of
the optical response of nano-object monolayers.
Abstract: The InP nanostructures have been fabricated by low-energy Ar+-ion of dose 1 × 1018 cm-2
and energy 50 keV, at normal incidence. The InP nanodot size varies from 50 to 90 nm.
Photoluminescence spectra show blue shifted visible emission band at 1.98 eV, and quenching of
the band edge emission from the nanopatterned surface. The blue-shifted emission band arises due
to size convoluted band-to-band emission form the surface nanodots while the defects formation in
the irradiated surface leads to the quenching of band edge emission. Thermal annealing results in
clustering of the patterned surface and enhancement of the band edge emission accompanied with
absence of visible band. Our results show that the origin of visible emission is from the surface
nanodots and not from the nanocrystallites in the implanted surface region. This is corroborated by
the wavelength dependence of photoluminescence measurement by probing different depth of the
Abstract: In recent years there have been extensive studies on III-V semiconductor quantum dots
(QDs). In this paper we have formulated the absorption spectra of a realistic QD system with dot
size distribution described by a Gaussian function. The dots were approximated as cubic boxes
having finite potentials at the boundaries. The effects of size non uniformity on the optical
absorption spectra of a realistic QD system was analyzed and the results have been compared with
ideal dots having infinite potentials at the boundaries.
Abstract: For successive annealing stages the photoluminescence (PL) peaks of InXGa1-XN/GaN
quantum wells (QWs) shift initially towards red which is followed by a blue. This phenomenon
contradicts the usual monotonic blueshift. We have found that the phenomena can be explained
properly only if we consider recombinations from the higher sub-bands to be present in the PL of
the InXGa1-XN/GaN QWs, which is not usual. When a strong piezoelectric field exists across a QW,
as encountered in InXGa1-XN/GaN QWs, the probability of optical transitions from higher sub-bands
of the QW become more probable. In this paper this theory has been established from experimental
Abstract: We demonstrated an experiment of femtosecond-laser damage threshold on GaAs wafer,
the damage threshold was measured from 50 to 400fs. The mechanism was discussed through
injection power, pulse duration and ablation profile. The results showed that the damage threshold
increased with the pulse duration, the relationship between diameter of ablation hole and laser
power density was also analyzed. It was concluded that the main factor affecting the damage
threshold was photon ionization and collision ionization.