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1
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From High Electron Mobility GaN/AlGaN Heterostructures to Blue-Violet InGaN Laser Diodes. Perspectives of MBE for Nitride Optoelectronics

100%
Skierbiszewski C.
Acta Physica Polonica A
|
2005
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vol. 108
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issue 4
635-651
EN
The recent progress in growth of nitride based semiconductor structures made by plasma assisted MBE is presented. This technology is ammonia free and nitrogen for growth is activated in RF plasma source from nitrogen molecules. The new growth mechanism - adlayer enhanced lateral diffusion of adatoms on semiconductor surface is studied in plasma assisted MBE. This mechanism enables us to achieve high quality step-flow epitaxy at temperatures 600-750ºC, much lower than expected from classical estimates based on the melting point of GaN. We show that growth at low temperatures in metal rich (gallium or indium) regime, together with use of low dislocation bulk GaN substrates, results in high quality of (In, Al, Ga)N layers and sharp interfaces. We demonstrate record high mobility of two-dimensional electron gas at GaN/AlGaN interface (with mobility exceeding 100 000 cm^2/(V s) at 4.2 K and 2500 cm^2/(V s) at 300 K) and report on first blue-violet InGaN multiquantum well laser diodes, operating in 407-422 nm wavelengths range. In this paper, we discuss also properties of strain compensated InAlN/InGaN multiquantum wells grown by plasma assisted MBE which are very attractive for telecommunication applications at 1.5μm wavelengths like electro-optical modulators or all-optical switches.
2
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Far-Infrared Narrow-Band Photodetector Based on Magnetically Tunable Cyclotron Resonance-Assisted Transitions in Pure n-Type InSb

52%
Dmowski L. H., Cheremisin M., Skierbiszewski C., Knap W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
733-736
EN
We present the possibility of using magnetic field to enhance responsivity and to tune spectral range of far-infrared InSb detector (based on photoconductivity effect) beyond its standard range limited to about 30 cm^{-1}. We show that due to cyclotron resonance assisted transitions we can use it as a tunable detector working up to energies about 180 cm^{-1} (22 meV). We have used such a detector as a spectrometer for measurements of the Landau emission from GaAs emitter.
3
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Evidence for Alloy Splitting of Ge Related DX State in Al_{x}Ga_{1-x}As

52%
Skierbiszewski C., Piotrzkowski R., Lubke K.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
531-533
EN
Thermal emission from resonant DX levels in Ge-doped GaAlAs was studied by measuring the temperature transients of free electron concentration. Pressure was used to fill the levels with electrons. Two emission peaks are observed in AlGaAs:Ge. This enables us to confirm that Ge, similarly to Si dopant, is stabilized upon dangling bond C_{3v} configuration in AlGaAs. Analysis of experimental data allows us to determine parameters of two components of the DX multilevel system. Evaluated alloy splitting of ground and top of the barrier states: 45 meV is comparable with determined for Si donor.
4
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Zero Field Spin Splitting in GaN/AlGaN Heterostructures Probed by the Weak Antilocalization

52%
Dybko K., Siekacz M., Skierbiszewski C.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1109-1113
EN
We present the magnetoconductivity measurements of a high mobility two-dimensional electron gas confined at GaN/AlGaN interface. The sensitive measurements of low field conductivity revealed both quantum corrections, the weak localization and antilocalization effects. It indicates the importance of the spin-orbit coupling in this wide band gap material. The analysis of the data provided the information about the temperature dependence of the dephasing time and total spin-orbit relaxation time. The conduction band spin splitting energy amounts to 0.23 meV and 0.35 meV at electron densities 2.2×10¹² cm¯² and 5.7×10¹² cm¯², respectively.
5
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Influence of Electric Field on Recombination Dynamics of Quantum Confined Carriers

52%
Korona K., Borysiuk J., Skierbiszewski C., Porowski S.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
243-247
EN
We present time-resolved photoluminescence measurements of GaN/AlGaN low dimensional structures showing very characteristic changes of dynamics related to strong electric field. Strong piezoelectric and spontaneous polarizations built-in in nitride structures lead to the changes in spatial separation of carriers which leads to changes in recombination energies and radiative lifetimes of the carriers. The observed effect can be well described by a simple exponential relation. The observed dependence can be explained by an approximated model of quantum-confined Stark effect based on the Airy functions.
6
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Electron Scattering and the Band Structure of Mixed Crystals Hg_{1-x}Fe_{x}Se

45%
Skierbiszewski C., Wilamowski Z., Suski T., Kossut J., Witkowska B.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
809-812
EN
In this paper the dependence of the band structure and the electron scattering mechanisms on the molar fraction x are studied in Hg_{1-x}Fe_{x}Se. The crossover from the zero-gap band to the open band-gap configuration at x ≈ 0.08 is predicted. We explain the drop of the electron mobility for x > 0.002 by the alloy scattering mechanism.
7
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Metastability of Localized Neutral Donor State In GaAs

45%
Skierbiszewski C., Jantsch W., Lübke K., Wilamowski Z., Suski T.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
905-908
EN
Investigations of the photoconductivity of GaAs:Ge under hydrostatic pressure show, in addition to the well known persistent photoconductivity due to the DX state, another giant photoconductivity caused by a neutral localised "A₁" state of the donor. We find that the top of the barrier for the electron recapture to the Α₁ state is pinned to the conduction band edge and the capture cross-section σ(T → ∞) is surprisingly small.
8
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A Model of Radiative Recombination in (In,Al,Ga)N/GaN Structures with Significant Potential Fluctuations

39%
Dróżdż P., Korona K., Sarzyński M., Czernecki R., Skierbiszewski C., Muzioł G., Suski T.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1209-1212
EN
The potential fluctuations in III-nitride quantum wells lead to many effects like emission broadening and S-shape energy vs. temperature dependence. The best description of the energy dependence comes from calculations based on Gaussian density of states. However, in most of the published reports, changes of carrier lifetime with energy and temperature are not taken into account. Since experimental evidence shows that lifetime significantly depends on energy and temperature, here we propose a model that describes two basic parameters of luminescence: lifetime of carries and emission energy as a function of temperature in the case of quantum wells and layers that are characterized by potential fluctuations. Comparison of the measured energy and lifetime dependences on temperature in specially grown InGaN/GaN quantum wells and InAlGaN layer shows very good agreement with the proposed theoretical approach.
9
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Pressure Study of Charged Donor Ordering in HgSe Doped with Iron and Gallium

39%
Skierbiszewski C., Suski T., Kossut J., Wilamowski Z., Dobrowolski W., Witkowska B.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
401-404
EN
Transport experiments (Hall effect and conductivity) under hydrostatic pressure up to 1 GPa at liquid helium temperatures on HgSe: Fe, Ga (N_{Fe} = 2 x 10^{19} cm^{-3}; 0 ≤ N_{Ga} ≤ 10^{19} cm^{-3}) were performed. The results show that the gallium co-doping of HgSe:Fe decreases the degree of spatial correlations between charged impurities. Under the hydrostatic pressure, used as a tool for changing the ratio of the charged to neutral impurities, this effect is even more pronounced. A qualitative agreement between the calculation within the short-range correlation model and our experimental data is achieved.
10
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Deep-Level Defects in MBE-Grown GaN-Based Laser Structure

39%
Tsarova T., Wosiński T., Mąkosa A., Skierbiszewski C., Grzegory I., Perlin P.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
331-337
EN
We present results of deep-level transient spectroscopy investigations of defects in a GaN-based heterostructure of a blue-violet laser diode, grown by plasma-assisted molecular beam epitaxy on a bulk GaN substrate. Three majority-carrier traps, T1 at E_C - 0.28 eV, T2 at E_C - 0.60 eV, and T3 at E_V + 0.33 eV, were revealed in deep-level transient spectra measured under reverse-bias conditions. On the other hand, deep-level transient spectroscopy measurements performed under injection conditions, revealed one minority-carrier trap, T4, with the activation energy of 0.20 eV. The three majority-carrier traps were revealed in the spectra measured under different reverse-bias conditions, suggesting that they are present in various parts of the laser-diode heterostructure. In addition, these traps represent different charge-carrier capture behaviours. The T1 trap, which exhibits logarithmic capture kinetics, is tentatively attributed to electron states of dislocations in the n-type wave-guiding layer of the structure. In contrast, the T2, T3, and T4 traps display exponential capture kinetics and are assigned to point defects.
11
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Electron-Electron Interaction Effects in Quantum Hall Regime of GaN/AlGaN Heterostructures

39%
Siekacz M., Dybko K., Maude D., Potemski M., Knap W., Skierbiszewski C.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
269-273
EN
We measured the activation of resistivity at quantum Hall minima in high mobility two-dimensional electron gas confined at AlGaN/GaN interface. The effective g-factor and effective mass was deduced. The electron-electron interactions modify both quantities compared to their bare band values. It is found that the influence of interactions is much more pronounced onto g-factor than effective mass. The relative spin susceptibility was also calculated and compared with available theories. The best agreement was found with the ideal two-dimensional gas model in random phase approximation.
12
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Near IR Refractive Index for GaInN Heavily Doped with Silicon

39%
Cywiński G., Kudrawiec R., Rzodkiewicz W., Kryśko M., Litwin-Staszewska E., Misiewicz J., Skierbiszewski C.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
936-938
EN
The authors report on growth and results of infrared measurements of GaInN heavily doped with silicon. The lattice matched to GaN epitaxial layer of Ga_{0.998}In_{0.002}N:Si has been grown in plasma assisted molecular beam epitaxy in the metal rich conditions. The room temperature Hall concentration and mobility of electrons are 2× 10^{20} cm^{-3} and 67 cm^{2}/(Vs), respectively. The refractive index has been determined by variable angle spectroscopic ellipsometry. The refractive index exhibited a significant reduction of its value (from 2.25 to 2 at 1.55 μm) at near IR range where are the main interests of potential applications for nitride based intersubband devices. Reported here values of refractive indices at 1.55 and 1.3 μm are appropriate for fabrication of cladding layers with the required contrast to GaN for intersubband devices. The observed drop of refractive index is attributed to the carrier-induced plasma edge effect, which has been directly observed in reflectance spectrum.
13
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Properties of Fe Doped β-HgS under Hydrostatic Pressure

33%
Szuszkiewicz W., Skierbiszewski C., Paszkowicz W., Dybko K., Domagała J., Dynowska E., Witkowska B., Zinn P.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
570-574
EN
High pressure- high temperature studies of the structural (zinc blende- cinnabar) phase transitions were performed in Hg_{1-x}Fe_{x} S mixed crystals (x<0.1) using synchrotron radiation and multianvil X-ray diffraction press. Pressure investigations of the Hall effect and conductivity of crystals containing up to a few percent of Fe were also performed at 295 K and 77 K. It was demonstrated that Fe in β-HgS creates deep, localized donor state resonant with the conduction band.
14
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Electrostatic Gates for GaN/AlGaN Quantum Point Contacts

33%
Czapkiewicz M., Cywiński G., Dybko K., Siekacz M., Wolny P., Gierałtowska S., Guziewicz E., Skierbiszewski C., Wróbel J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1026-1028
EN
We report on AlGaN/GaN quantum point contacts fabricated by using e-beam lithography and dry ion etching. The tunable nano-constrictions are defined by the integration of side and top gates in a single device. In this configuration, the planar gates are located on the both sides of a quantum channel and the metallic top gates, which cover the active region, are separated from the substrate by an insulating and passivating layers of HfO_2 or Al_2O_3/HfO_2 composite. The properties of devices have been tested at T = 4.2 K. For side gates we have obtained a very small surface leakage current I_g< 10^{-11} A at gate voltages |V_g| < 2 V, however, it is not enough to close the quantum channel. With top gates we have been able to reach the pinch-off voltage at V_g = - 3.5 V at a cost of I_g ≈ 10^{-6} A, which has been identified as a bulk leakage current.
15
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Waveguide Design for Long Wavelength InGaN Based Laser Diodes

33%
Muzioł G., Turski H., Siekacz M., Sawicka M., Wolny P., Cheze C., Cywiński G., Perlin P., Skierbiszewski C.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1031-1033
EN
One-dimensional optical waveguide calculations were performed to study the dependence of waveguide design on confinement factor (Γp) and optical losses (α_i) of nitride laser diodes for emission wavelength ranging from 405 nm to 520 nm. We found that the conventional waveguide design containing GaN waveguide and AlGaN cladding layers known from violet laser diode does not support sufficient confinement of the optical mode for long wavelength devices (λ > 450 nm). We proposed a new design consisting of a thick InGaN waveguide which enhances the confinement. We compared the theoretical predictions with laser diodes grown by plasma assisted molecular beam epitaxy.
16
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Weak Antilocalization in Quantum Wells

33%
Knap W., Skierbiszewski C., Litwin-Staszewska E., Kobbi F., Zduniak A., Robert J., Pikus G., Iordanskii S., Mosser V., Zekentes K.
Acta Physica Polonica A
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1995
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vol. 87
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issue 2
427-432
EN
Spin relaxation in degenerated two-dimensional (2D) electron gas is studied by measurements of the magnetic field dependence of the weak an­tilocalization corrections to the conductivity in GaInAs quantum wells. Con­sistent quantitative (up to order of magnitude) description of weak antilocal­ization data on GaAs like heterojunctions and quantum wells was obtained. Our results show that spin precession around the effective magnetic field direction as described by the Dyakonov-Perel model is the main spin relax­ation mechanism in degenerated 2D electron gas in semiconductors with no inversion symmetry.
17
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Two-Electron DX State in CdTe:In

33%
Skierbiszewski C., Wiśniewski P., Litwin-Staszewska E., Suski T., Wilamowski Z., Zakrzewski A., Karczewski G., Jantsch W.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
927-930
EN
In this paper we investigate electron emission/capture from/to the DX state of indium in CdTe by means of high pressure freeze-out cycle and steady-state photo-conductivity experiments. The results indicate that the DX state is occupied by two electrons. A comparison with deep level transient spectroscopy data shows that two-electron emission occurs at low temperatures, while one-electron emission takes place at high temperatures.
18
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Stimulated Emission from the MBE Grown Homoepitaxial InGaN Based Multiple Quantum Wells Structures

27%
Ivanov V., Godlewski M., Miasojedovas S., Juršėnas S., Kazlauskas K., Žukauskas A., Skierbiszewski C., Siekacz M., Leszczyński M., Perlin P., Suski T., Grzegory I.
Acta Physica Polonica A
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2005
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vol. 107
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issue 2
225-229
EN
We report on photoluminescence characterization of InGaN based laser structures grown by homoepitaxial radio frequency plasma-assisted molecular beam epitaxy. Owing to Si doped barriers, the structures show a negligible impact of the built-in electric field, which was proved by excitation intensity dependent and quantum well width dependent luminescence experiments. Relatively low variation in band potential due to inhomogeneous distribution of In was quantitatively estimated from the photoluminescence temperature behavior using Monte Carlo simulation of in-plane carrier hopping and optically detected cyclotron resonance experiments. Efficient stimulated emission with a low threshold for optically pumped laser structures was observed.
19
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Optically Pumped Laser Action on Nitride Based Separate Confinement Heterostructures Grown along the (11¯20) Crystallographic Direction

27%
Teisseyre H., Szymański M., Khachapuridze A., Skierbiszewski C., Feduniewicz-Żmuda A., Siekacz M., Łucznik B., Kamler G., Kryśko M., Suski T., Perlin P., Grzegory I.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
467-472
EN
The intention of this work is to discuss and report on our research on nonpolar laser structures grown on bulk GaN crystal substrates along the (11¯20) nonpolar direction. The main advantages of such nonpolar structures are related to the elimination of the built-in electric fields present in commonly used systems grown along the polar (0001) axis of nitride crystals. We demonstrated the optically pumped laser action on separate confinement heterostructures. Laser action is clearly shown by spontaneous emission saturation, abrupt line narrowing, and strong transversal electric polarization of output light. The lasing threshold was reached at an excitation power density of 260 kW/cm^2 for a 700μm long cavity (at room temperature).
20
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High Power Continuous Wave Blue InAlGaN Laser Diodes Made by Plasma Assisted MBE

27%
Skierbiszewski C., Siekacz M., Wiśniewski P., Perlin P., Feduniewicz-Żmuda A., Cywiński G., Smalc J., Grzanka S., Grzegory I., Leszczyński M., Porowski S.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
345-351
EN
Room temperature, continuous wave operation of InGaN multi-quantum wells laser diodes made by rf plasma assisted molecular beam epitaxy at 411 nm wavelength is demonstrated. The threshold current density and voltage were 4.2 kA/cm^2 and 5.3 V, respectively. High optical power output of 60 mW was achieved. The lifetime of these laser diodes exceeds 5 h with 2 mW of optical output power. The laser diodes are fabricated on low dislocation density bulk GaN substrates, at growth conditions which resembles liquid phase epitaxy. We demonstrate that relatively low growth temperatures (600-700°C) pose no intrinsic limitations for fabrication of nitride optoelectronic components by plasma assisted molecular beam epitaxy.
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