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Introduction
Publications
Publications (32)
With the sub-bandgap optical excitation, thermal dynamics of holes among multiple levels in n-type GaN epilayers with different dopants of Si, Ge and C are investigated via measuring and modelling variable-temperature yellow luminescence (YL) band of the samples. In sharp contrast to the case of above-bandgap optical excitation, the variable-temper...
We report luminescence decay characteristics of the InGaN/GaN scintillator heterostructures doped
with Zn. Unusually large shifting of luminescence band caused by Zn acceptors incorporated in InGaN
is observed both in time-resolved and excitation-dependent spectra. Origins of the shifts are discussed,
and model based on donor-acceptor pair recombin...
This work suggests new morphology for the AlGaN/GaN interface which enhances electron mobility in two-dimensional electron gas (2DEG) of high-electron mobility transistor (HEMT) structures. The widely used technology for the preparation of GaN channels in AlGaN/GaN HEMT transistors is growth at a high temperature of around 1000 °C in an H2 atmosphe...
The InGaN multiple quantum wells (MQW) samples with the undoped and Si doped GaN barriers were grown by Metal Organic Vapour Phase Epitaxy (MOVPE). By comparing defects-related emission bands in the undoped GaN and InGaN layers, one may conclude that the band is complex in the InGaN layer, composed of at least two contributions peaking at 2.17 and...
To better understand the scintillation properties of gallium nitride, a detailed characterization of Metal Organic Vapour Phase Epitaxy (MOVPE) grown GaN layers doped with Ge is conducted. This study includes the measurements of radioluminescence and photoluminescence spectra, thermally stimulated luminescence and photoluminescence as well as scint...
A set of GaN layers prepared by metalorganic vapor phase epitaxy under different technological conditions (growth temperature carrier gas type and Ga precursor) were investigated using variable energy positron annihilation spectroscopy (VEPAS) to find a link between technological conditions, GaN layer properties, and the concentration of gallium va...
Metal Organic Vapour Phase epitaxy (MOVPE) grown GaN layers doped with Si were studied by means of radio-, photo- and thermally stimulated luminescence, scintillation decay kinetics, as well as electron paramagnetic resonance. Two luminescence bands were observed: the narrow and fast peaking at about 3.45 eV (ascribed to excitons) and the broad and...
A huge acceleration of the yellow band defect luminescence (YB) with increasing Si and Ge doping concentration in GaN layers has been observed and studied. The donor doping concentrations in the n-type GaN varied from 5 × 1016 cm⁻³ to 1.5 × 1019 cm⁻³ for undoped, Si-doped, and Ge-doped samples. Consequently, the fastest component of the photolumine...
Two sets of InGaN/GaN MOVPE-grown samples were studied by high-resolution X-ray diffraction techniques together with statistical analysis of AFM images in order to determine the impact of In concentration and threading dislocations density on the V-pit formation. It was shown that in our samples, the density of V-pits in the epilayer matched the thr...
Zn contamination of InGaN/GaN multiple quantum well (MQW) structure from unknown source is found. A model describing concentration profile of Zn acceptor impurity in InGaN/GaN MQW structure is introduced and compared to measured values. The model is based on difference among the formation energies of acceptors in the InGaN quantum wells. A nice cor...
Nitride heterostructures with an extremely high number of InGaN/GaN multiple quantum wells (MQWs) were grown and studied by multiple techniques. Large redshift (282 meV) in photoluminescence (PL) spectra was observed with an increasing number of quantum wells (QWs) in the structure from 10 to 60. From the comparison of structures grown on sapphire...
A stack of five Al(Ga)N-based quantum wells is investigated by combined laterally and depth resolved cathodoluminescence (CL) spectroscopy in order to distinguish lateral and vertical inhomogeneities of these wells. Transmission electron microscopy (TEM) micrographs provide data for the real sample structure, which enters into the Monte-Carlo simul...
Set of samples based on InGaN/GaN multiple quantum wells structures with extremely thick active region and high QW numbers was prepared on different substrates by Metal Organic Vapour Phase Epitaxy. Their morphology was studied by SEM images and their optical properties, including photoluminescence excitation, photoluminescence emission spectra and...
This work suggests new alternative explanation why a single InGaN quantum well (QW) or the deepest QWs in the multiple quantum well (MQW) structures suffer with a high non-radiative recombination rate. According to SIMS results, positron annihilation spectroscopy and photoluminescence measurements we suggest that vacancy of Ga in complex with hydro...
In this work the mechanism which helps to reduce the dislocation density by deposition of a SiNx interlayer is discussed. It is shown that the dislocation reduction by SiNx interlayer deposition is influenced by dislocation density in the underlying GaN layers. The SiNx interlayer is very effective when the original dislocation density is high, whi...
The aim of this work is to compare and improve optical and structural properties of GaN layers prepared using TMGa or TEGa precursors. MOVPE grown GaN buffer layers on sapphire substrates are usually grown from TMGa precursor at the temperatures above 1000 °C. These layers contain deep and shallow acceptor levels which are responsible for blue and...
The aim of this work is to elucidate how different growth mode and composition of barriers can influence the QW properties and their PL and to find optimal QW capping process, to suppress the In desorption from QWs and to maintain the QW PL efficiency. It concentrates on the technology procedure for growth of upper quantum well (QW) interfaces in I...
InGaN/GaN multiple quantum well structures are studied as a potential candidate for superfast scintillation detectors showing the leading decay time around 1 ns and an intense luminescence. Photoluminescence properties of these structures with quantum well (QW) number ranging from 10 to 60 are described and discussed. It is shown that with increase...
Although InGaN layers or InGaN/GaN superlattices are commonly used as efficiency improving buffers for LED structure production, there is still a controversy and active discussion about the mechanisms improving the luminescence properties of InGaN QWs grown above such buffers. In this manuscript it is shown that presence of In in the buffer layer i...
In this work, the influence of Si doping position on the photoluminescence (PL) properties of InGaN/GaN quantum wells (QWs) is studied. A set of samples with different positions of Si doping with respect to the multi quantum well (MQW) active region was prepared and studied by PL, SIMS and AFM and structure band alignments were simulated. Based on...
In this work we investigate the epitaxial growth of boron containing (Al,Ga)N layers and superlattices for applications in the active region of UV‐LEDs. For AlBN layers containing 5% of boron as quantified by secondary ion mass spectrometry, columnar growth has been observed. Transmission electron microscopy (TEM) studies revealed B‐lean, crystalli...
In this work we compare luminescence results obtained on InGaN/GaN multiple quantum well (QW) structures with 10 and 30 QWs. The aim is to increase the intensity of faster blue QW emission and decrease the luminescence of the QW defect band, showing a slower luminescence decay time, which is undesired for fast scintillator applications. We demonstr...
We have optimized technology of GaN buffer layer growth with respect to the application in fast scintillation structures. The deep defect luminescence so called yellow band (YB) with decay time up to tens of microseconds is undesired for these applications and should be suppressed or at least the ratio of intensities of excitonic to YB maximum has...
