In this paper we present modification of angular photoresponse of InGaAsN-based photodiode with applied polymer (IPDIP) three-dimensional (3D) woodpile structure. 3D woodpile structure was prepared as effective diffractive element for using in optoelectronic devices with possibility of direct application on a chip surface. 3D woodpile structure was prepared using laser lithography by direct laser writing process. The effect of woodpile structure on angular photoresponse structure was investigated from goniophotometer measurements. Spatial modulation of light coupling into the photodiode chip with applied 3D woodpile structure was documented for irradiation by broad-band green light.
Progress in nanotechnologies accelerated the polymer based photonics, where simple and cheap solutions often bring comparable and sometimes also novel interesting results. Good candidates are polymer photoresists and siloxane materials with unique mechanical and optical properties. We present laser lithography as efficient tool for fabrication of different three-dimensional (3D) structures embedded in polydimethylsiloxane (PDMS) membranes. Presented concept of PDMS based thin membranes with 3D structures works as an effective diffraction element for modification of radiation pattern diagram of light emitting diodes and changes also the angular photoresponse of photodiodes. All these results were demonstrated on two types of 3D structures – spheres arranged in cubic lattice and woodpile structure.
In this paper application of Si3N4, AlN and polyimide to passivate GaAsN/GaAs MSM photodetectors is presented. The
MSM structures were made on the undoped GaAsN epitaxial layers in which concentration of nitrogen was varied from
1.0 to 2.6 %. The dark and illuminated I-V characteristics of the devices are presented. Comparison of the dark current
value and photoresponse obtained, for selected wavelengths in visible and IR range, from the MSM devices with
different passivation layers is provided. Measurements of the dark current and photoresponse in the unpassivated and
passivated MSM structures allowed to estimate relation between the bulk and surface components of the dark current.
Therefore crystal quality of the epitaxial layers grown in different process conditions could be compared.
Dilute nitride (In, Ga)(As, N) alloys grown on GaAs substrate are a very attractive materials for optoelectronics. In this
work we compare the optical properties of (In, Ga)(As, N)/GaAs triple quantum well grown by atmospheric pressure
metal organic vapour phase epitaxy. As grown and annealed structures were investigated by means of
photoluminescence and contactless electroreflectance spectroscopies. Energies of fundamental transition from each
measurement were determined and compared, moreover the value of Stokes shift was assigned and discussed.
We have investigated deep-level defects in InGaAsN/GaAs 3xQW structures by means of conventional as well as high-resolution
deep level transient spectroscopy (DLTS). The three samples were grown by atmospheric pressure
metalorganic vapour phase epitaxy (AP-MOVPE) in different growth temperatures (566°C, 575°C and 585°C). The DLTS measurements revealed four electron traps E1 (0.17-0.24 eV), E2 (0.36-0.38 eV), E3 (0.46-0.49 eV) and E4 (0.81-0.84 eV) and one hole trap H1(0.8 eV) in our structures. The electron trap E1 was associated with N-related complexes
while the other electron traps with native defects, usually observed in GaAs-based structures EL6, EL3 and EL2,
respectively. Finally, the trap E2 and H1, observed in the structure grown at lowest temperature, were associated with the
same trap, which can act as both an electron and hole trap. It was thus concluded that E2/H1 may be a generation-recombination
GaAsN and InGaAsN semiconductor alloys with a small amount of nitrogen, so called dilute nitrides, are especially
attractive for telecom lasers and very efficient multijunction solar cells applications. The epitaxial growth of these
materials using MBE and MOVPE is a big challenge for technologists due to the large miscibility gap between GaAs and
GaN. Additionally, elaboration of the growth process of quaternary alloys InGaAsN is more complicated than GaAsN
epitaxy because a precise determination of their composition requires applying different examination methods and
comparison of the obtained results. This work presents the influence of the growth parameters on the properties and alloy
composition of the triple quantum wells 3×InGaAsN/GaAs grown by atmospheric pressure metal organic vapour phase
epitaxy AP MOVPE. Dependence of the structural and optical parameters of the investigated heterostructures on the
growth temperature and the nitrogen source concentration in the reactor atmosphere was analyzed. Material quality of
the obtained InGaAsN quantum wells was studied using high resolution X-Ray diffraction HRXRD, contactless electro-reflectance
spectroscopy CER, photoluminescence PL, secondary ion mass spectrometry SIMS, photocurrent PC and
Raman RS spectroscopies, deep level transient spectroscopy DLTS and transmission electron microscopy TEM.
Over the last few years, ternary and quaternary semiconductor compounds containing (Ga, In) and (N, As) elements
become subject of many studies. Both, indium and nitrogen, lowers the band gap of gallium arsenide, but their influence
on lattice parameter is compensated. As a result it is possible to deposit epitaxial layers of 1 eV , or less, material which
is matched to GaAs substrate. GaAs technology is well known and much cheaper than more sophisticated phosphorus
alloys. Optoelectronic devices composed of dilute nitrides materials can be widely used as a telecommunication lasers,
photodetectors or even photovoltaic cells.
Investigated samples were performed using atmospheric-pressure MOVPE system with AIXTRON AIX200 R-and-D
reactor. GaNAs layers were deposited as bulk layers, while GaInNAs material grown as bulk and additionally as
quantum wells with GaAs barriers. Gallium arsenide substrates were utilized.
Studies were performed utilizing Raman spectroscopy at room temperature. Phonons were excited using 514 nm Ar+
laser. Characteristic for such structures GaN-like local vibrational mode was observed to change its position with
changing nitrogen concentration. GaAs-like longitudinal optic phonon also was investigated. As a result an attempt to
measure nitrogen concentration in mentioned materials using Raman spectroscopy was performed.
Heterostructures of GaInNAs/GaAs multiple quantum wells were characterized by high resolution x-ray diffraction.
Complexity and stress compensating effect of such quaternary alloys cause many characterization problems. One of the
most important issue is determination of composition of the material, which cannot be performed utilizing only one
characterization method. That is why structural analysis had to be related with optical measurements which give different
information correlated with composition. A comparison of theoretical calculations of energy band gap with energy of
transitions in GaInNAs QWs from photoluminescence or contactless electro-reflectance measurements supplement the
results of HRXRD and gives complete information about the structure required as a feedback to develop technology of
heterostructures epitaxial growth.
Photoreflectance (PR) spectroscopy has been applied to the investigation of Si (delta) -doped AlxGa1-xAs layers grown by metal-organic vapor phase epitaxy on GaAs substrates. Measurements have been carried out on samples with aluminum content of 0,0.35 and 1. The observation of Franz-Keldysh oscillations (FKO) in a number of more than 10 (in the best case) and application of the fast Fourier transformation has allowed us to determine the internal electric field with high accuracy. Thus, the potential barrier between surface and (delta) -doped region has been estimated. Finally, the contribution of heavy and light hole related transitions to the FKO has been resolved.
Experimental set-up has been established by using high resolution monochromator as well as He-Ne and Ar multiline lasers. Epitaxial, undoped and doped (Si and Zn) GaAs and GaAlAs layers as well as heterostructures of GaAs/GaAlAs have been grown in atmospheric pressure vertical MOCVD system. Room temperature photoreflectance (PR) have been applied to characterize layers, heterostructures as well as the multiple quantum wells. The surface and interface related PR have been studied by means of Kramers-Kronig analysis. Decomposition of PR spectrum into the spectra connected with surface region and with the interface has been proposed. Modulus of the complex photoreflectance gives us the critical point energy, whereas the phase of this function can be used for a carrier concentration topography.