Fabrication and photosensitivity of AgInSe2/III-VI isotypic heterojunctions

AgInSe₂ thin films on glass substrates have been prepared by pulsed laser deposition. Rectifying heterojunctions with a pronounced photovoltaic effect have been fabricated for the first time by placing such films in optical contact with layered III-VI (InSe, GaSe) semiconductors. The maximum photosensitivity of such heterostructures is 10–10³ V/W. It is concluded that the prepared structures can be used as wideband selective photoreceivers. Fiz. Tekh. Poluprovodn. 33, 1205–1208 (October 1999)     

Photosensitivity of porous silicon-layered III–VI semiconductors heterostructures

Rectifying heterojunctions with photosensitivity 1–5 V/W at T=300 K were obtained by forming optical contacts between free porous silicon and layered InSe and GaSe semiconductors. A wide-band photovoltaic effect was obtained when these heterostructures were illuminated on the free porous silicon plate side. The long-wavelength photosensitivity edge of these devices is determined by direct transitions in InSe or GaSe, respectively. It is concluded that heterojunctions based on free porous silicon plates can be used as wide-band phototransducers. Fiz. Tekh. Poluprovodn. 32, 353–355 (March 1998)     

Oxide-<Emphasis Type="Italic">p</Emphasis>-InSe heterostructures with improved photoelectric characteristics

Heterostructures consisting of p-InSe and native oxide were formed by thermal oxidation of indium selenide crystals in air. Long-term (for 1–5 days) oxidation of InSe substrates at 450°C leads to changes in both the photosensitivity spectral band and the photoelectric parameters of the heterostructures compared to samples oxidized for 5–15 min. These changes are due to the layer-by-layer formation of additional oxide phases on the semiconductor surface. For the best heterostructures, the open-circuit voltage attains 0.6 V and the short-circuit current density is 30–35 mA/cm² under saturation conditions. The electrical characteristics of the heterostructures are distorted by the effect of series resistance, which complicates the determination of the potential-barrier height and the mechanism of current flow through the barrier.     

Prompt quality monitoring of InSe and GaSe semiconductor crystals by the nuclear quadrupole resonance technique

To determine the quality of layer-structured semiconductor single crystals, the nuclear quadrupole resonance technique with successive scanning of the entire sample volume and assessment of the structural quality on the basis of the observed spectra is used. The proposed method is appropriate in the case of InSe, GaSe and GaAs ingots grown in evacuated cells by the Bridgman technique and can be used repeatedly in subsequent technological procedures with no operator access to the material. To provide scanning within a limited region of the sample and to ensure efficient interaction of the high-frequency field with the crystal, excitation and detection of the nuclear-spin-induction signal is implemented by the saddle-shaped transceiver coil of the nuclear quadrupole resonance spectrometer.     

Artificial GeSi substrates for heteroepitaxy: Achievements and problems

It is desirable to have a set of substrates which are based on Si and ensure growth of heterostructures with various lattice parameters in order to develop electronic devices composed of semiconductor materials whose epitaxial growth is reasonably well developed. Such substrates are typically referred to as artificial. In this paper, a comparative analysis of various methods for the fabrication of artificial substrates (heterostructures), in which the relaxation of stresses is based on the introduction of misfit dislocations, is performed. Based on published and new experimental data, the mechanisms for attaining a low density of threading dislocations in plastically relaxed films represented by heterostructures composed of GeSi and an Si buffer layer grown at low temperatures are analyzed. The problems and results of another group of methods for obtaining artificial substrates which gained favor recently and become known as “compliant” or “soft” substrates are discussed. The most important electrical parameters of Si and GeSi films grown on artificial substrates are considered.     

Quantum wires and dots show the way forward

Concluding his three-part series on the pivotal role of compound semiconductor heterostructures, Professor Alferov of the Ioffe Institute in St. Petersburg reviews the development and recent exciting advances in quantum wires and, in more detail, quantum dot structures. The future trends and perspectives of these new types of heterostructures are discussed.     

Realization of Quantum Hall Effect in Chemically Synthesized InSe

Recently, 2D electron gases have been observed in atomically thin semiconducting crystals, enabling the observation of rich physical phenomena at the quantum level within the ultimate thickness limit. However, the observation of 2D electron gases and subsequent quantum Hall effect require exceptionally high crystalline quality, rendering mechanical exfoliation as the only method to produce high‐quality 2D semiconductors of black phosphorus and indium selenide (InSe), which hinder large‐scale device applications. Here, the controlled one‐step synthesis of high‐quality 2D InSe thin films via chemical vapor transport method is reported. The carrier Hall mobility of hexagonal boron nitride (hBN) encapsulated InSe flakes can be up to 5000 cm² V^?1 s^?1 at 1.5 K, enabling to observe the quantum Hall effect in a synthesized van der Waals semiconductor. The existence of the quantum Hall effect in directly synthesized 2D semiconductors indicates a high quality of the chemically synthesized 2D semiconductors, which hold promise in quantum devices and applications with high mobility.     

Photoelectric properties of structures based on TlInS2 single crystals

The photovoltaic effect in heterocontacts of various types, viz., In/TlInS₂, InSe/TlInS₂, and GaSe/TlInS₂, is investigated. The relative photoconversion quantum efficiency of these structures is studied as a function of the energy of the incident photons and the polarization plane of linearly polarized light. It follows from photosensitivity measurements that the photosensitive structures obtained can be employed as broad-band and selective photosensors of optical radiation. Fiz. Tekh. Poluprovodn. 32, 78–81 (January 1998)     

Electroluminescence of InGaAs/GaAs quantum-size heterostructures with (III,Mn)V and Ni ferromagnetic injectors

Electroluminescence characteristics of light-emitting diodes based on InGaAs/GaAs quantum well heterostructures with an injector layer made of ferromagnetic metal (Ni), semimetal compound (MnSb), or magnetic semiconductor (InMnAs) were comparatively studied. The general feature is electroluminescence quenching as the spacer layer thickness between a quantum well and a magnetic injector decreases. It was found that the temperature dependence of the electroluminescence in diodes with Ni and MnSb is caused by thermal ejection of carriers from the quantum well; in diodes with InMnAs, it is caused by the temperature dependence of the carrier concentration in magnetic semiconductor and thermal ejection of carriers from the quantum well in the high-temperature region.     

Photovoltaic effect in a-Si:H/n-InSe heterostructures

Heterostructures in an a-Si:H/InSe system were grown by the deposition of a-Si:H films onto the surface (001) of InSe single-crystal wafers and also by deposition of pure indium films with their subsequent selenization, in which case InSe films were synthesized at the a-Si:H surface. The photovoltaic effect was observed and studied for both types of heterostructures. It was concluded that the heterostructures obtained may be used as wide-band photoconverters of radiation.     

InSe Schottky Diodes Based on Van Der Waals Contacts

2D semiconductors are excellent candidates for next‐generation electronics and optoelectronics thanks to their electrical properties and strong light‐matter interaction. To fabricate devices with optimal electrical properties, it is crucial to have both high‐quality semiconducting crystals and ideal contacts at metal‐semiconductor interfaces. Thanks to the mechanical exfoliation of van der Waals crystals, atomically thin high‐quality single‐crystals can easily be obtained in a laboratory. However, conventional metal deposition techniques can introduce chemical disorder and metal‐induced mid‐gap states that induce Fermi level pinning and can degrade the metal‐semiconductor interfaces, resulting in poorly performing devices. In this article, the electrical contact characteristics of Au–InSe and graphite–InSe van der Waals contacts, obtained by stacking mechanically exfoliated InSe flakes onto pre‐patterned Au or graphite electrodes without the need for lithography or metal deposition is explored. The high quality of the metal‐semiconductor interfaces obtained by van der Waals contact allows to fabricate high‐quality Schottky diodes based on the Au–InSe Schottky barrier. The experimental observation indicates that the contact barrier at the graphite–InSe interface is negligible due to the similar electron affinity of InSe and graphite, while the Au–InSe interfaces are dominated by a large Schottky barrier.     

The effect of neutron radiation on the photoelectric parameters of ITO-GaSe structures

The effect of 1-MeV neutrons on the photoelectric parameters of ITO-GaSe heterostructures was studied. It is shown that the observed variations in the current-voltage characteristics are caused by the effect of penetrating radiation on both components of the structure, which brings about an increase in the resistance of the heterostructures. The presence of exciton fine structure in the photosensitivity spectra after irradiation indicates that GaSe retains high structural quality notwithstanding the introduced radiation defects. The results obtained are accounted for by spatial redistribution of doping impurity in GaSe and structural changes in the ITO films.     

Simulation of capacitance-voltage characteristics of heterostructures with quantum wells using a self-consistent solution of the Schrödinger and Poisson equations

Methods are developed for calculating capacitance-voltage characteristics and finding the concentration profile of free charge carriers in semiconductor doped heterostructures containing a quantum well. The capacitance-voltage characteristic of a heterostructure with a quantum well was calculated using a numerical self-consistent solution of the Poisson and Schrödinger equations in the context of a unified quantum-mechanical approach. The suggested method was applied to the simulation and analysis of the experimental capacitance-voltage characteristics of heterostructures with strained InGaAs/GaAs quantum wells.     

The history and future of semiconductor heterostructures

The history of the development of semiconductor heterostructures and their applications in various electron devices is presented, along with a brief historical survey of the physics, production technology, and applications of quantum wells and superlattices. Advances in recent years in the fabrication of structures utilizing quantum wires and especially quantum dots are discussed. An outline of future trends and prospects for the development and application of these latest types of heterostructures is presented. Fiz. Tekh. Poluprovodn. 32, 1–18 (January 1998)     

Interlayer Transition in a vdW Heterostructure toward Ultrahigh Detectivity Shortwave Infrared Photodetectors

Van der Waals (vdW) heterostructures of 2D atomically thin layered materials (2DLMs) provide a unique platform for constructing optoelectronic devices by staking 2D atomic sheets with unprecedented functionality and performance. A particular advantage of these vdW heterostructures is the energy band engineering of 2DLMs to achieve interlayer excitons through type‐II band alignment, enabling spectral range exceeding the cutoff wavelengths of the individual atomic sheets in the 2DLM. Herein, the high performance of GaTe/InSe vdW heterostructures device is reported. Unexpectedly, this GaTe/InSe vdWs p–n junction exhibits extraordinary detectivity in a new shortwave infrared (SWIR) spectrum, which is forbidden by the respective bandgap limits for the constituent GaTe (bandgap of ≈1.70 eV in both the bulk and monolayer) and InSe (bandgap of ≈1.20–1.80 eV depending on thickness reduction from bulk to monolayer). Specifically, the uncooled SWIR detectivity is up to ≈10¹⁴ Jones at 1064 nm and ≈10¹² Jones at 1550 nm, respectively. This result indicates that the 2DLM vdW heterostructures with type‐II band alignment produce an interlayer exciton transition, and this advantage can offer a viable strategy for devising high‐performance optoelectronics in SWIR or even longer wavelengths beyond the individual limitations of the bandgaps and heteroepitaxy of the constituent atomic layers.     

Optical properties of metamorphic hybrid heterostuctures for vertical-cavity surface-emitting lasers operating in the 1300-nm spectral range

The possibility of fabricating hybrid metamorphic heterostructures for vertical-cavity surfaceemitting lasers working in the 1300-nm spectral range is demonstrated. The metamorphic semiconductor part of the heterostructure with a GaAs/AlGaAs distributed Bragg reflector and an active region based on InAlGaAs/InGaAs quantum wells is grown by molecular-beam epitaxy on a GaAs (100) substrate. The top dielectric mirror with a SiO₂/Ta₂O₅ distributed Bragg reflector is formed by magnetron sputtering. The spectra of the room-temperature microphotoluminescence of these vertical-cavity surface-emitting laser heterostructures are studied under 532-nm excitation in the power range of 0–70 mW (with a focused-beam diameter of ~1 μm). The superlinear dependence of the photoluminescence intensity on the excitation power, narrowing of the photoluminescence peaks, and a change in the modal composition may be indications of lasing. The results obtained give evidence that the technology of the metamorphic growth of heterostructures on GaAs substrates can be used for the fabrication of vertical-cavity surface-emitting lasers working in the 1300- nm spectral range.     

Piezoelectric effects in semiconductor heterostructures: applications and consequences

The piezoelectric (PZ) effect in strained semiconductor heterostructures can be used as an additional degree of freedom in designing novel heterostructures with desired optoelectronic properties. After a short review of previous work in the field, we discuss two examples in which the presence of the PZ field is either beneficial or unwelcome. First, we present a wavelength-tunable laser diode whose tuning mechanism is based on the quantum confined Stark effect and we show that the tuning range of the device can be significantly enhanced if the active quantum well contains a PZ field. Next, we discuss the case of nitride heterostructures where unwanted polarization-induced electric fields limit seriously their performance in optoelectronic applications. We show that the use of quaternary nitrides can help circumvent this problem.     

硅基发光材料研究进展

阐述了等电子杂质、掺Er硅、硅基量子结构(包括量子阱、量子线和量子点)及多孔硅的发光机理,综述了90年代以来a-Si/SiO2、SiGe/Si等Si基异质结构材料的优异特性和诱人的应用前景,着重介绍了能带工程为Si基异质结构带来的新特性、新功能,重点介绍了硅基量子点的制备和发光机理,综述了半导体量子点材料的最新发展动态和发展趋势。     

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.     

Strong Interlayer Transition in Few-Layer InSe/PdSe2 van der Waals Heterostructure for Near-Infrared Photodetection

Near infrared (NIR) photodetectors based on 2D materials are widely studied for their potential application in next generation sensing, thermal imaging, and optical communication. Construction of van der Waals (vdWs) heterostructure provides a tremendous degree of freedom to combine and extend the features of 2D materials, opening up new functionalities on photonic and optoelectronic devices. Herein, a type-II InSe/PdSe₂ vdWs heterostructure with strong interlayer transition for NIR photodetection is demonstrated. Strong interlayer transition between InSe and PdSe₂ is predicted via density functional theory calculation and confirmed by photoluminance spectroscopy and Kelvin probe force microscopy. The heterostructure exhibits highly sensitive photodetection in NIR region up to 1650 nm. The photoresponsivity, detectivity, and external quantum efficiency at this wavelength respectively reaches up to 58.8 A W⁻¹, 1 × 10¹⁰ Jones, and 4660%. The results suggest that the construction of vdWs heterostructure with strong interlayer transition is a promising strategy for infrared photodetection, and this work paves the way to developing high-performance optoelectronic devices based on 2D vdWs heterostructures.