D. Radziewicz

Photoreflectance study of δ-doped semiconductor layers by a fast Fourier transformation

Abstract Photoreflectance (PR) spectroscopy has been applied to the investigation of Si δ-doped GaAs, Al 0.35 Ga 0.65 As and AlAs layers grown by metal–organic vapor phase epitaxy (MOVPE) on GaAs substrates. The observation of Franz–Keldysh oscillations (FKO) and the application of fast Fourier transform (FFT) has allowed us to determine the internal electric field and, hence, the potential barrier between surface and δ-doped region of the layer. The FFT of the photoreflectance spectra has exhibited two separate heavy and light hole frequencies showing that the FKO in the PR signal are always the superposition of these two components.

Determination of indium and nitrogen contents of InGaAsN quantum wells by HRXRD study supported by BAC calculation of the measured energy gap

Determination of indium and nitrogen content in InGaAsN quantum wells (QWs) is often based on the analysis of high-resolution X-ray diffraction (HRXRD) measurements. The comparison of diffraction curves of two similar samples, with and without nitrogen, together with an assumption of constant indium incorporation efficiency during the growth of layers with and without nitrogen, may lead to a large deviation in the determined In and N content. The HRXRD curve simulations supported by bandgap determination and calculations seem to be a solution of this problem. Comparison of the results achieved from simulated HRXRD curves with the calculations of all QWs transitions measured by contactless electro-reflectance (CER) can lead to reduction of deviations in composition determination of InGaAsN quantum wells. The proposed algorithm was applied for investigation of InGaAsN QWs grown by atmospheric pressure metalorganic vapor phase epitaxy (APMOVPE).

Technology and characterisation of GaAsN/GaAs heterostructures for photodetector applications

The nitrogen-containing conventional AIIIBV semiconductor alloys, so-called diluted nitrides (AIIIBV-N), have been extensively studied recently. Unusual properties of these materials make them very promising for applications in lasers and very efficient multijunction solar cells. This work presents the technology and properties of undoped GaAs1-xNx/GaAs heterostructures used as active regions in the construction of metal-semiconductor-metal (MSM) photodetectors. The atmospheric pressure metal organic vapour phase epitaxy (APMOVPE) was applied for growing MSM test structures. Their structural and optical properties were examined using high resolution X-ray diffraction (HRXRD), photoluminescence (PL), and photoreflectance spectroscopy (PR). Chemical wet etching was applied for forming an active region and a multifinger Schottky metallization was used as MSM contacts. Dark and illuminated current-voltage characteristics were measured. Based on the obtained results, the main detector parameters as responsivity and spectral response were estimated

MOVPE technology and characterisation of silicon δ-doped GaAs and AlxGa1−xAs

Abstract This work presents the investigation of MOVPE growth of silicon δ-doped GaAs and AlxGa1−xAs epilayers and different methods used for their characterisation. The influence of the growth temperature, SiH4 flow rate and AlxGa1−xAs composition on δ-doping characteristics is discussed. Properties of the Si δ-doped structures were examined using capacitance–voltage (C–V) measurements, photoreflectance spectroscopy, micro-photoluminescence, micro-Raman and photocurrent spectroscopies.

Growth of high-quality GaN and AlxGa1-xN layers by an MOVPE technique

AlxGa1-xN layers with 0.02 xGa1-xN layer grown on it were evaluated by high resolution X-ray measurements, their surface morphology was observed with SEM and Nomarski optical microscope. Electrical properties of the layers were determined by C-V measurements performed at 100 kHz and 1 MHz using mercury probes. The aluminum incorporation into the solid phase during the growth process has been studied. As a result high quality AlxGa1-xN/GaN layers for electronic application have been deposited.

Influence of the AP MOVPE process parameters on properties of (In, Ga)(As, N)/ GaAs heterostructures for photovoltaic applications

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.

Influence of rapid thermal annealing on optical properties of (In, Ga)(As, N)/GaAs quantum wells

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.

Epitaxial Growth and Characterisation of Silicon Delta-Doped GaAs, AlAs and Alx Ga1-xAs

Investigation of MOVPE growth of silicon δ-doped GaAs, AlAs and Al x Ga 1-x As epilayers and different methods used for their characterisation are presented. The epitaxial structures were grown in an atmospheric pressure horizontal AIX 200 Aixtron reactor. Delta doping was formed by SiH 4 introduction during the growth interruption. The influence of the growth temperature and Al x Ga 1-x As composition on delta-doping characteristics, carrier concentration and mobility is discussed. Properties of the investigated Si δ-doped structures were examined using capacitance-voltage measurements, Van der Pauw-Hall measurements (300K, 77K), photocurrent measurements, photoreflectance spectroscopy and X-ray measurements.

Study of the nature of light hole excitonic transitions in InGaAs/GaAs quantum well

Abstract Photoreflectance (PR) spectra of strained In GaAs/GaAs MQWs were measured. Heavy and light hole excitonic transitions were observed. Applying results of theoretical calculations which include excitonic and strain effects, we obtained that the existence of type II light hole exciton in our type I MQW system should be considered.

Electro-optical properties of diluted GaAsN on GaAs grown by APMOVPE

In this paper we report on the optical and electrical studies of single GaAs1−xNx epitaxial layers grown on GaAs substrates by means of atmospheric pressure metal organic vapour phase epitaxy (APMOVPE). Three kinds of samples with 1.2 %, 1.6 % and 2.7 % nitrogen content were studied. Optical properties of the layers were investigated with the use of room temperature transmittance and reflectance measurements. Subsequently Schottky Au-GaAs1−xNx contacts were processed and characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements within 80–480 K temperature range. From the I-V and C-V characteristics the ideality factor, series resistance and built-in potential were determined. Obtained diodes can be used for further studies on defects with the use of DLTS method.