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.
This paper reports the fabrication of n-type crystalline Si based solar cell using boron liquid solution (BLS) deposited by spray method for p-type emitter formation. The X-ray photoelectron spectroscopy (XPS) was used for the analysis of surface composition and electronic states of elements at the glass layer of dopant (GLD) obtained from BLS. The investigation of the borosilicate glass layer (BSG) created on a base of GLD during diffusion process were carried out by transmission electron microscopy (TEM). The diffusion profiles were determined by secondary ion mass spectrometry (SIMS) and electrochemical capacitance-voltage (EC-V) techniques, whereas the solar cells were characterized by the light current-voltage (I-V) and spectral measurements. The influence of a doping process on a minority carrier lifetime of the Si wafers was detected by quasi-steady-state photoconductance technique. Application of the elaborated BSL allowed to obtain the p-type Si emitters from BSG layer which exhibits unproblematic etching behaviour after diffusion process and final fabrication of the solar cells with the fill factor of 74% and photoconversion efficiency of 13.04 %. The elaborated BLS is a source which offers an attractive practicable alternative to form emitters on the n-type Si substrate.
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.
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.
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.
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.