K. D. Moiseev

Interface-induced optical and transport phenomena in type II broken-gap single heterojunctions

This review deals with a study of optical and magnetotransport phenomena at a type II arsenide–antimonide heterojunction with a broken-gap alignment. A fundamental feature of this structure is partial overlapping of the InAs conduction band with the GaSb-rich solid solution valence band. In such a heterostructure, electrons and holes are spatially separated and localized in self-consistent quantum wells formed on both sides of the heterointerface. This leads to unusual tunnelling-assisted radiative recombination transitions and novel transport properties. Results of a pioneering study of interface-related luminescence in type II broken-gap GaInAsSb/InAs heterostructures, with a high quality abrupt heteroboundary, grown by the LPE method, are presented. The energy band diagram of the type II broken-gap GaInAsSb/InAs(GaSb) heterostructures and band overlapping control, depending on a doping level and epilayer composition of quaternary solid solution, are discussed. A 2D-electron channel with high Hall mobility at the p-GaInAsSb/p-InAs interface was found and examined. A great deal of attention is paid to quantum transport properties of the semimetal channel in a wide magnetic field range (up to 18 T) at low temperatures. A cyclotron resonance study was used to obtain data on the energy spectrum at the interface and to estimate effective masses for subbands in the semimetal channel. The intriguing behaviour of the 2D-electron system in the presence of localized holes in high magnetic fields and the first observation of integer quantum Hall effect plateaus on the type II single GaInAsSb/InAs heterointerface formed by LPE are demonstrated. A tunnelling-injection laser with high asymmetric band offset confinements based on the type II broken-gap heterojunction is considered. Applications of the interface-induced phenomena in luminescent and transport properties for the design of novel mid-IR optoelectronic devices and Hall sensors are briefly reviewed.

A 2.78-μm laser diode based on hybrid AlGaAsSb/InAs/CdMgSe double heterostructure grown by molecular-beam epitaxy

A mid-IR laser based on a hybrid pseudomorphic AlGaAsSb/InAs/CdMgSe heterostructure with a III–V/II–VI heterovalent interface at the 0.6-μm-InAs active region has been fabricated by molecular-beam epitaxy on p+-InAs substrate. It provides ∼1.5-eV asymmetric barriers for both electrons and holes in InAs, inhibiting carrier leakage from the active region. Despite a nonoptimal defect density at the CdMgSe/InAs interface (106–107u2002cm−2), the structure demonstrates lasing at ∼2.78 μm (up to 100 K) under pulse injection pumping with the threshold current density of 3–4 kA/cm2. The proposed design is promising for high-power mid-IR lasers operating at room temperature.

Quantum magnetotransport at a type II broken-gap single heterointerface

Abstract We report the study of quantum magnetotransport in a semimetal channel at the type II broken-gap single heterointerface at magnetic field range up to 16 T at low temperature. The GaIn0.16As0.22Sb/InAs heterostructures with high quality abrupt heteroboundary (∼12 A) were fabricated by liquid phase epitaxy (LPE) on InAs substrates. Electron channel with high carrier mobility ( μ H =50 000–70 000 cm2/Vxa0s) was found at the interface in the isotype p-GaInAsSb/p-InAs heterostructure under low magnetic field up to 5 T. Three series of Shubnikov–de Haas oscillations in Hall conductivity and magnetoresistance were observed under high magnetic fields (9–16 T) at T=1.45 K. Two of them were corresponded to 2D-electron subbands E1 and E2 with carrier concentration n 1 =4.77×10 11 cm −2 and n 2 =1.82×10 11 cm −2 , while the significant contribution of the third one corresponding to 2D-hole subband with concentration p∼1012 cm−2 has been pronounced in the range 13–16 T. The most impressed result is the observation of the integer quantum Hall effect (QHE) plateaus in the Hall conductivity with the filling factor ν=2, 3 and 6 when ultraquantum limit for E1 subband was realized. It is the first demonstration of QHE in a type II single GaInAsSb/InAs heterostructure with self-consistent quantum wells grown by LPE.

Photovoltaic detector based on type II p-InAs/AlSb/InAsSb/AlSb/p-GaSb heterostructures with a single quantum well for mid-infrared spectral range

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.

Interface photoluminescence in type II broken-gap P–Ga0.84In0.16As0.22Sb0.78/p-InAs single heterostructures

Mid-infrared photoluminescence has been observed from interface transitions in high quality, abrupt P–Ga0.84In0.16As0.22Sb0.78/p-InAs heterojunctions grown by liquid phase epitaxy from an In-rich melt. The Ga0.84In0.16As0.22Sb0.78 quaternary epitaxial layer was unintentionally doped and grown lattice matched on to a (100) oriented p-type InAs substrate, resulting in a P–p isotype heterojunction. The photoluminescence emission spectra were investigated and exhibited three pronounced emission bands in the spectral region from 0.30 to 0.68 eV; hν1=0.317 eV, hν2=0.380 eV, and hνL=0.622 eV. The emission band hν1 was identified with radiative transitions between electron and hole quantum well subbands in the semimetal channel at the P–GaIn0.03As0.10Sb/p-InAs interface, while the hν2 band originates from radiative transitions involving deep acceptor states in the InAs substrate. The high-energy recombination hνL is characteristic of the Ga0.84In0.16As0.22Sb0.78 bulk quaternary layer.

Type II heterostructures with InSb quantum dots inserted into p-n InAs(Sb,P) junction

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.

Room-temperature electroluminescence of AlSb∕InAsSb single quantum wells grown by metal organic vapor phase epitaxy

Intense mid-infrared (λ∼2μm) room temperature electroluminescence from metal organic vapor phase epitaxy (MOVPE) grown type-I single AlSb∕InAsSb∕AlSb quantum wells (QWs) is reported. The spectral position of the electroluminescent peaks is in good agreement with k∙p envelope function calculation in the frame of four-band Kane’s model taking into account the intermixing of s and p states in the deep quantum well. A four times increase of the emission intensity with temperature increasing from 77to300K can be explained by highly efficient radiative recombination of the electrons injected into the narrow AlSb∕InAsSb∕AlSb QW due to its specific design, leading to Auger process suppression.

Electroluminescence of confined carriers in type II broken-gap p-GaInAsSb/p-InAs single heterojunction

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.

InSb quantum dots and quantum rings in a narrow-gap InAsSbP matrix

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.

Suppression of Auger recombination in the diode lasers based on type II InAsSb/InAsSbP and InAs/GaInAsSb heterostructures

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.