We report on study of electrical and optical properties of type II heterostructures with InSb quantum dots (QDs) inserter
into the InAs-based p-n junction made by LPE-MOVPE combine method. InSb QDs were grown on an InAs(100)
substrate by LPE. Overgrowth on the surface with the self-assembled InSb QD arrays was performed by MOVPE using
capping layers based on binary InAs and quaternary InAsSb solid solutions. High-resolution cross-sectional image of the
InSb QDs buried into the InAs(Sb,P) matrix was obtained for the first time by transmission electron microscopy.
Structural parameters of the InSb QDs such as size, shape and internal strain were demonstrated and discussed. The
uniform small QDs with high density (>1010 cm-2) with dimensions of 3 nm in height and 14 nm in diameter were found
to be self-assembled and dislocation-free without any extended defects, whereas the low-density large QDs (108 cm-2)
with dimensions of 10 nm in height and 50 nm in diameter were relaxed and demonstrated interface strain with the InAs
substrate. I-V characteristics of the mesa-diode heterostructures with the InSb QDs inserted into InAs p-n junction were
studied at the wide temperature range T=77-300 K. Intense positive and negative electroluminescence for both n-InAs/p-
InAs and n-InAs/InSb-QDs/p-InAs heterostructures was found in the spectral range 3-4 μm. Evolution of the spectra in
dependence on applied external bias (forward and reverse) were observed at 77 K and 300 K.
We report a study of InSb quantum dots and quantum rings grown on InAs(100) substrate by LPE-MOVPE combine
method. Characterization of InSb/InAs(Sb,P) quantum dots was performed using atomic force microscopy and
transmission electron microscopy. The bimodal growth of uncapped InSb quantum dots was observed in the temperature
range T=420-450 °C. The low-density (5×108 cm-2) large quantum dots with dimensions of 12-14 nm in height and 45-50
nm in diameter are appeared at 445 °C, whereas high-density (1×1010 cm-2) dislocation-free small quantum dots with
dimensions of 3-5 nm in height and 11-13 nm in diameter were obtained at 430 °C. Capping of the InSb quantum dots by
binary InAs or InAsSbP epilayers lattice-matched with InAs substrate was performed using MOVPE method. Tunnel-related
behavior in a forward curve of I-V characteristics was observed in heterostructures with buried InSb quantum
dots inserted in InAs p-n junction. Evolution of electroluminescence spectra on driving current at negative bias and
suppression of negative luminescence from buried InSb/InAs quantum dots were found out in the spectral range 3-4 μm
at 300 K. Deposition from the InSb melt over the InAsSb0.05P0.10 capping layer resulted in the formation of InSb quantum
rings with outer and inner diameters about 20-30 nm and 15-18 nm respectively. Surface density of the quantum rings of
2.6×1010 cm-2 was reached at 430 °C.
Mid-infrared photovoltaic detector (PD) designed on the base of a type II p-InAs/p-GaSb asymmetric heterostructure
with a deep AlSb/InAsSb/AlSb quantum well (QW) at the interface is reported. The heterostructures containing the
single QW were grown by LP-MOVPE. Transport, electroluminescent and photoelectrical properties of these structures
were investigated. Intense both positive and negative electroluminescence was observed in the spectral range 3-4 µm
above room temperature (300-400 K). Spectral response in the mid-infrared range 1.2-3.6 μm was obtained at
temperatures T=77-300 K. High quantum efficiency η=0.6-0.7 responsivity Sλ=1.4-1.7 A/W and detectivity
Dλ* =3.5×1011 cm Hz1/2w-1 were achieved at 77 K. Such QW PDs are suitable for heterodyne spectroscopy and free
space communication using quantum cascade lasers as well as for gas analysis and ecological monitoring applications.
The observation of the Quantum Hall effect (QHE) in a semimetal channel with coexisting electrons and holes, simultaneously, at the type II broken-gap p-GaIn0.16As0.22Sb/p-InAs single heterointerface based on unintentionally doped quaternary solid solution obtained by liquid phase epitaxy (LPE) was reported for the first time elsewhere. In this report the quantum magnetotransport in the p-Ga0.84In0.16As0.22Sb0.78/p-InAs single heterostructure has been studied for a set of the samples with the both undoped and doped with Zn impurity quaternary layer at low temperatures in high magnetic fields up to 14 T.
We have proposed a new physical approach for the design of mid-IR lasers operating at λ = 3.2 - 3.26 μm based on type II heterojunctions with a large asymmetric band-offset at the interface (ΔEC > 0.6 eV and ΔEV > 0.35 eV). These high potential barriers produce effective electron-hole confinement at the interface and results in a tunnel-injection radiative recombination mechanism within the device due to reduce leakage current from the active region. The creation of high barriers for carriers leads to their strong accumulation in the active region and increases quantum emission efficiency of the spatially separated electrons and holes across the heteroboundary. Our approach also leads to the suppression of non-radiative Auger-recombination and a corresponding increase in the operation temperature of the laser. The active region of the laser structure consists of the type II heterojunction formed by narrow-gap In0.83Ga0.17As0.82Sb0.18 (Eg = 0.393 eV at 77 K) and wide-gap Ga0.84In0.16As0.22Sb0.78 (Eg = 0.635 eV at 77 K) layers lattice-matched to InAs substrate.
We present a novel hybrid laser structure based on III-V and II-VI compounds combining some advantages of type I and type II heterojunctions in one heterostructure. Such design allows the achievement of large energy offsets at the interface in the conduction and the valence band exceeding of 1.0 eV in order to provide good electron and hole confinement. P-AlAsSb/n-InAs/N-Cd(Mg)Se laser heterostructures were grown on p-InAs substrates by original technology of MBE method in two separate growth chambers consequently. Photoluminescence spectra included tow emission bands at hv=0.41 eV and hv=2.08 eV associated with InAs and CdMgSe bulk recombination transitions, respectively. Intense electroluminescence was observed at (lambda) =2.73micrometers (77K) and (lambda) =3.12micrometers (300K). Weak temperature dependence of spontaneous emission indicated the effective carrier confinement in the InAs layer due to large potential barriers ((Delta) sEc=1.28eV and (Delta) EV=1.68eV). Proposed hybrid III-V/II-VI heterostructure is very promising for creation the mid-infrared lasers with improved performances operating in the spectral range of 3- 5micrometers .
There is considerable interest in the realization of room temperature mid-infrared diode lasers for a variety of applications, including remote gas sensing, infrared countermeasures and molecular spectroscopy. However the maximum temperature of operation in narrow gap III-V component alloys is limited by strong non-radiative Auger recombination and various band structure engineering techniques are being investigated to provide Auger suppression. In our work we are investigating the possibility of obtaining a practical 3.3micrometers laser by making use of radiative recombination across single type II hetero-interfaces. Because transitions occur between confined electron and hole states localized on either side of the heterojunction where the potential wells are triangular, there exists the possibility of tailoring the wave-function overlap to give good Auger suppression while still maintaining high radiative output. At the same time growth form the liquid phase offers potentially lower SRH recombination. We compared two such heterojunctions (InAs0.94Sb0.06/InAs and Ga0.96In0.04As0.11Sb0.89/ InAs) grown by rapid slider LPE and report on the photoluminescence and electroluminescence from the interfaces. The dependence of these interface transitions on temperature, excitation intensity, band offset and polarization is reported, with a view towards incorporating these in the active region of a practical laser.
We have proposed a new physical approach to design mid-IR lasers based on type II heterostructures with strong asymmetric band offset confinement at the interface. It allows to create the high barriers for carriers and to reduce leakage current from an active region, that leads to increase the quantum efficiency of the emission due to the strong accumulation of recombining carriers. Here this approach was successfully used for fabrication high power lasers operating at (lambda) equals 3.26 micrometers . The laser structure containing narrow-gap active InGaAsEb (Eg equals 0.380 eV) layer and wide-gap confined InAsSbP (Eg equals 0.520 eV) and GaInAsSb (Eg equals 0.640 eV) layers lattice-matched to InAs substrate was grown by LPE. Such heterostructure has the band energy diagram with strong asymmetric band offsets and allows to provide high barriers for electrons at the InGaAsSb/GaInAsSb heterointerface ((Delta) Ec equals 0.60 eV) and for holes at the InGaAsSb/InAsSbP one ((Delta) Ev equals 0.15 eV). Maximum output power of 1.5 W was achieved in pulsed mode with pulse duration 1 microsecond(s) and repetition rate 100 Hz for 100 micrometers broad area laser with cavity length about of 1000 micrometers . Threshold current density was about 450 A/cm2. Characteristic temperature T0 equals 47 K was observed in the range of 77 - 140 K.
Comparative study of threshold current temperature dependence, differential quantum efficiency and light polarization was performed for type I and type II InAsSb/InAsSbP heterostructures as well as for tunneling- injection GaInAsSb/InGaAsSb laser based on this type II broken-gap heterojunction. Experimental evidence of non- radiative Auger-recombination suppression in type II InAsSb/InAsSbP heterolasers with high band-offset ratio (Delta) Ev/(Delta) Ec equals 3.4 was obtained. Reduction of temperature dependence of the threshold current was demonstrated for both kinds of type II lasers. Maximum operation temperature and characteristic temperature T equals 203 K with T0 equals 40 K and T equals 195 K with T0 equals 47 K were achieved for type II InAsSb/InAsSbP and tunneling- injection p-GaInAsSb/n-InGaAsSb lasers, respectively.
First observation of electroluminescence in type II broken-gap p-GaInAsSb/p-InAs single heterojunctions is reported. Intensive spontaneous emission was obtained under applied bias at T equals 77 - 300 K. Two narrow `resonant' emission bands were observed in the spectral range 3 - 5 micrometers at T equals 77 K with full width at half maximum about 1 - 2 kT. It was established that effect of unusual electroluminescence in isotype type II broken-gap p-p- heterostructure due to indirect (tunnel) radiative recombination of spatial separated 2D- electrons and holes localized in deep adjacent quantum wells at different sides of the interface. Novel tuneable mid-infrared light sources are proposed.
The phase diagram of the quaternary AlInAsSb system has been investigated. These data have been used for LPE growth of the AlxIn1-xAsySb1-y solid solutions lattice-matched to InAs (with Al mole percentage in the range 0.0-0.08). A band gap was determined for this material in dependence on the composition by photoluminescence measurements. The band gap of the solid solution in the investigated range of composition corresponds to a wavelength from 3 micrometers (x equals 0.0, Eg equals 0.414 eV) to 2.5 micrometers (x equals 0.08, Eg equals 0.49 eV).
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