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.

https://iopscience.iop.org/article/10.1088/0268-1242/19/10/R03/pdf

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

We report on a powerful 4.6 ?m light emitting diode (LED), operating at room temperature, suitable for carbon monoxide gas detection. The source is based on a InAs0.55Sb0.15P0.30 /InAs0.89Sb0.11/InAs0.55Sb0.15P0.30 symmetrical double heterostructure with large band offsets. To improve performance, the InAs0.89Sb0.11 ternary material in the active region was purified by using rare-earth ion gettering during liquid phase epitaxial growth. A pulsed optical output power in excess of 1 mW at room temperature has been measured, making these emitters suitable for use in cost-effective instruments for the environmental monitoring of carbon monoxide. The Auger coefficient of the InAs0.89Sb0.11 active region material was evaluated by analysis of the temperature quenching of the LED output power measured at constant current. It was found to be C0 = 1.5 ? 10-26 cm6 s-1 with an activation energy of E = 31 meV, which is in good agreement with previous findings in the literature.

http://iopscience.iop.org/article/10.1088/0022-3727/32/24/304/pdf

High power 4.6 µm light emitting diodes for CO detection

The demand for large-scale deep learning neural networks has driven the development of nanoscale memristor devices, which perform brain-inspired neuromorphic computing. In this study, we present an electroforming free-tunneling junction device based on a TiN/SiOx/p-Si structure. This proposed device exhibited artificial synapse behaviors via applying pulse train. The impacts of pulse amplitude, width and interval were investigated for gradually modulating the conduction of the device. Particularly, short-term plasticity (STP) could be continually modulated by successive voltage sweeps or pulses. Symbolizing the relaxation time of memory ability could emulate the excitatory postsynaptic current (EPSC) of different pulse models. It is proposed that the variable-range hopping (VRH) and Fowler–Nordheim (FN) tunneling theories are responsible for gradual conduction change to mimic the bio-synapse based in the TiN/SiOx/p-Si memristor. This study provides further insights into the physical mechanisms of the gradual change in resistance for mimicking bio-synapse.

Synapse behavior characterization and physical mechanism of a TiN/SiOx/p-Si tunneling memristor device

A series of optically pumped type-II quantum-well “W” lasers with wavelengths ranging from 5.4 to 7.3 μm operated at temperatures up to at least 220 K for pulsed operation. The peak output power at 80 K was 1.1 W/facet for a device emitting at λ=7.0 μm. Internal losses were characterized for the temperature range between 40 and 190 K. Auger coefficients determined from an analysis of the threshold pump intensities were found to be suppressed by up to an order of magnitude compared to type-I III–V semiconductors with the same energy gaps.

Type-II quantum-well “W” lasers emitting at λ=5.4–7.3 μm

We have measured and calculated effective masses m* and the band structure of the In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As quantum well on the InP substrate with one or two InAs inserts in the quantum well and GaAs inserts in heterointerface barriers. The effective mass m* was measured by the Shubnikov?de Haas effect. Double symmetric InAs inserts in a quantum well lead to decreasing of m* by about 10%?35% as compared with the uniform In0.53Ga0.47As lattice-matched quantum well.

https://iopscience.iop.org/article/10.1088/0268-1242/27/3/035021/pdf

Electron effective masses in an InGaAs quantum well with InAs and GaAs inserts

Type II antimonide–arsenide based heterostructures have recently received great attention from researchers engaged in the design of mid-infrared optoelectronic devices. Magnetotransport properties of the semimetal channel and the interface electroluminescence were experimentally studied on type II broken-gap GaInAsSb/InAs single heterojunctions grown by LPE with high quality interface. An electron channel with high Hall mobility was, for the first time, observed at the interface of isotype p-GaInAsSb/p-InAs heterojunctions with undoped and slightly doped quaternary layers at low temperatures. A depletion of the electron channel was found to be due to the heavy acceptor doping level of the quaternary layer. The two-dimensional nature of the interface carriers was established by Shubnikov–de Haas oscillation experiments at 1.8–4.2 K under magnetic fields up to 9–14 T. Intensive interface electroluminescence in the structures under study was observed in the spectral range of 3–4 µm at low temperatures (4.2–77 K). A model of the recombination transition at the type II broken-gap interface was proposed and experimentally confirmed. A new physical approach to the design of mid-infrared tunnelling-injection lasers is demonstrated.

Interface-induced phenomena in type II antimonide-arsenide heterostructures

Quantum magnetotransport at a type II broken-gap single heterointerface

Specific features of the energy spectrum of a separated type-II heterojunction in an external magnetic field are studied theoretically and experimentally. It is shown that, due to hybridization of the states of the valence band of one semiconductor and the conduction band of the other semiconductor at the heterointerface, there are level anticrossings, which produce quasigaps in the density of states in a nonzero magnetic field. The experimental results of magnetotransport studies for the GaInAsSb/p-InAs quaternary solid solutions with different doping levels are shown to agree well with the results of simulation, and specific features of the energy spectrum of separated type-II heterojunctions are established.

Energy spectrum and quantum magnetotransport in type-II heterojunctions

Spin-dependent electron transport in a type II GaInAsSb/p-InAs heterojunction doped with Mn in quantized magnetic fields

High magnetic field magnetoresistance and quantum Hall effect (QHE) in type II broken-gap Ga 1-x In x Sb 1-y As y /p-InAs single heterostructures based on undoped or doped with Zn and Te quaternary epilayers have been investigated to determine the effect of the carrier concentration and doping type on the 2D-electron density and quantum conductivity. The two-dimensional nature of quantum oscillations was established from the angular dependence of Shubnikov-de Haas (SdH) oscillations and observation of the QHE plateaus in the Hall conductivity in high magnetic fields when the upper electronic sub-bands become empty. We have observed maxima of σ xy (H) between the quantised Hall states at the filling factors v= 1, 2, and 3. The QHE plateau-to-plateau transitions from v= 3 to v= 2 and from v= 2 to v= 1 were different from the ones corresponding to one-type carrier. Doping of the epilayer alters the band bending for holes and electrons at the heteroboundary and results in changes of the electron concentration and SdH period according to the filling of the multi sub-band structure for the electron channel.

R. V. Parfeniev

Papers

Interface-induced phenomena in type II antimonide-arsenide heterostructures

Quantum magnetotransport at a type II broken-gap single heterointerface

Energy spectrum and quantum magnetotransport in type-II heterojunctions

Spin-dependent electron transport in a type II GaInAsSb/p-InAs heterojunction doped with Mn in quantized magnetic fields

Two‐dimensional semimetal channel in a type II broken‐gap GaInAsSb/InAs single heterojunction