Group III-V Compound Semiconductor Research Articles

Synthesis and Tuning of Electronic, Optical, and Photoelectrochemical Properties of Copper Metavanadate Alloys via Alkaline Earth Metal Substitution

Unlike the well-studied and technologically advanced Group III-V and Group II-VI compound semiconductor alloys, alloys of ternary metal oxide semiconductors have only recently begun to receive widespread attention. Here, we describe the effect of alkaline earth metal substitution on the optical, electronic, and photoelectrochemical (PEC) properties of copper metavanadate (CuV2O6). As a host, the Cu-V-O compound family presents a versatile framework to develop such composition-property correlations. Alloy compositions of A0.1Cu0.9V2O6 (A = Mg, Ca) photoanodes were synthesized via a time and energy-efficient solution combustion synthesis (SCS) method. The effect of introducing alkaline earth metals (Mg, Ca) on the crystal structure, microstructure, electronic, and optical properties of copper metavanadates was investigated by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), and Raman spectroscopy. The PXRD, TEM, and Raman spectroscopy data demonstrated the polycrystalline powder samples to be mutually soluble, solid solutions of copper and alkaline earth metal metavanadates and not simple mixtures of these compounds. The DRS data showed a systematic decrease in the optical bandgap with Cu incorporation. These trends were corroborated by electronic band structure calculations. Finally, the PEC properties exhibited a strong dependence on the alloy composition, pointing to possible applicability in solar water splitting, heterogeneous photocatalysis, phosphor lighting/displays, and photovoltaic devices.

Modeling Insights Into the Assembly Challenges of Focal Plane Arrays

Ongoing technological advances in photodetector material growth and processing, readout integrated circuits, and robust hybridization (packaging) methods for assembling high-resolution and small-pitch size pixel arrays are the main enabling factors for pushing the frontiers of high-performance Focal Plane Array (FPA) technologies for imaging systems. This paper details the development of analytical and numerical models and demonstrates their use to generate insights into the feasibility of two flip-chip assembly processes for packaging infrared (IR) detector chips. The modelling studies focus on the challenges of forming the indium interconnection arrays in the case of the FPA technologies using Group III-V compound semiconductor materials and ultra-fine pitch pixel array layouts. The accurate alignment of the IR detector chip onto the readout chip in the case of high-density pixel architectures is a critical requirement for the packaging process. To gain better understanding of this requirement, which has a clear implication for the quality and subsequent reliability performance of the FPA, compression and reflow bonding process models are developed using suitable modeling approaches and methods and then demonstrated for two distinctive focal plane array design configurations. The novelty of this work is in the developed modeling capabilities utilizing different computational methods, from large deformation and contact analysis finite element to energy-based and harmonic motion mechanics, to characterize and optimize the mechanical and dynamic non-linear behavior of the indium solder joints and their formation during FPA packaging. The feasibility of bonding techniques for different resolution FPAs and under flip-chip misalignment conditions is assessed. The modeling results pointed to a very strict, sub-micrometer flip-chip placement accuracy requirement for the assembly of FPAs with ultra-fine indium bump array resolution.

Ultrasensitive UV-C detection based on MOCVD-grown highly crystalline ultrawide bandgap orthorhombic κ-Ga2O3

Orthorhombic κ-Ga2O3, as one of the Ga2O3 polymorphs, is considered a promising as ultrawide bandgap material for extreme environment devices. It is considered more superior than the conventional group III-V compound semiconductors and silicon carbides in extreme environments demanding material/device characteristics of high-voltage, high-temperature, high-pressure, high-impact, and high-radiation. In this study, we demonstrate ultrasensitive ultraviolet-C (UV-C) detection using Si-doped orthorhombic κ-Ga2O3 photodetectors. A 150 nm thick κ-Ga2O3 film was grown on a 2-inch diameter sapphire (α–Al2O3) wafer via metal organic chemical vapor deposition (MOCVD) method. The crystallinity of orthorhombic κ-Ga2O3 film was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The ultrawide bandgap of approximately 4.9 eV was confirmed by UV transmittance measurement. For UV-C detection analysis, a planar device with a channel length of 20 μm was fabricated using Au/Ti metal contacts on the orthorhombic κ-Ga2O3 film. The device doped under 15 sccm SiH4 flow rate showed ultrahigh photoresponse of ∼72.1 A/W, Ion/Ioff of ∼14, and decent rise (∼0.35 s) and decay (∼1.79 s). Our results will contribute to the understanding on a new material phase of κ-Ga2O3, as well as on developing optoelectronics devices with high radiation hardness suitable for operation in extreme environments.

Analysis of Surface Reaction for Group III-V Compound Semiconductors in Functional Water

Group III–V compound semiconductors are attracting attention as new channel materials that have higher carrier mobility than Si. However, defects easily occur at the interface between the semiconductor and insulator film, which degrades performance. In an earlier study, we demonstrated that the interfacial properties of InP are degraded by the growth of In2O3 and that In2O3 grows better in water than in air. Therefore, it is necessary to suppress the growth of In2O3 to improve the interfacial properties of InP. In this work, we focused on functional water, which can be controlled by adjusting the water conditions, and investigated the growth behavior of In2O3 in functional water. As a result, we found that the growth is suppressed in the low-pH range and in hydrogen water. It is important that H+ ions reduce OH− ions, which contributes to the reaction with InP.

Dermal absorption of gallium antimonide in vitro and pro-inflammatory effects on human dermal fibroblasts

Gallium antimonide (GaSb) is a group III-V compound semiconductor with a comparatively narrow band gap energy (0.73 eV at 300 K) that allows efficient operation in the near-infrared region. This property may be useful in developing new biomedical instruments such as epidermal optoelectronic devices. The present study investigated the absorption of GaSb in pig skin in vitro for 24 h using Franz cells. A donor solution was prepared by soaking GaSb thin films in synthetic sweat. The results showed that both gallium and antimony penetrated the skin, and permeation and resorption occurred for gallium. Histopathological findings showed no inflammatory responses in pig skin exposed to GaSb for 24 h. Cytotoxicity was significantly elevated after 3 and 7 days, and pro-inflammatory cytokines and IL-8 levels were low after 1 and 3 days but elevated 7 days following the direct culturing of human dermal fibroblasts (HDF) on GaSb thin films. These results demonstrate that the short-term cytotoxicity and pro-inflammatory effect of GaSb on HDF were relatively low.

(Invited) Heteroepitaxy and Strain Engineering of Germanium-Silicon-Tin Ternary Alloy Semiconductor Thin Films for Energy Band Design

Ternary alloy semiconductor of germanium-silicon-tin (GeSiSn) has attracted for electronic and optoelectronic applications, because this group-IV alloy material provides energy band engineering independent on the lattice constant like group III-V compound semiconductors [1]. In addition, GeSiSn/Ge(Sn) heterostructure realizes type-I energy band alignment with a sufficiently large band offset at both conduction and valence band edges with no or very small lattice mismatching [2,3], and that is preferable for effective carrier confinement for light emitting devices and high mobility transistors. On the other hand, there are still challenges for crystal growth with strain and band engineering of group-IV ternary alloy semiconductor thin films. GeSn is one of promising candidates for optoelectronic applications since it realizes direct transition group-IV semiconductor. GeSn with an in-plane lattice constant larger than Ge is better to enhance the emission efficiency, as the conduction band edge of the gamma-valley lowers than that of the L-valley with large lattice constant and/or in-plane tensile strain. Thus, a buffer layer such as GeSiSn with a lattice constant sufficiently larger than Ge is required to obtain direct transition GeSn thin films, and lattice-constant engineering technology of buffer and GeSn layers should be developed with well-controlled strain relaxation technique. Recently, we explored effective strain engineering technique of GeSiSn ternary alloy epitaxial layers on Ge and Si substrate to obtain much larger in-plane lattice constant. We investigated the effect of low-temperature growth of Ge buffer layer on the strain relaxation of GeSiSn layer [4,5]. Also, we examined the ion implantation technique into substrate to enhance the strain relaxation of GeSiSn epitaxial layers grown on Ge substrate [6]. We can achieve GeSiSn epitaxial layers with the enhancement of strain relaxation and the lattice constant larger than Ge, although the crystalline quality of these epitaxial layers should be still improved. We previously reported that the strain direction as compressive and tensile ones is significantly influence of GeSiSn epitaxial layers [7]. The control of strain structure and its relaxation process is keys to obtain high crystalline quality of GeSiSn and GeSn heteroepitaxial layers for improving the electronic and optoelectronic properties of group-IV heterostructures.

Thermal and nonthermal melting of III-V compound semiconductors

We study theoretically the response of group III-V compound semiconductors (AlAs, AlP, GaAs, GaP, GaSb) to free-electron laser irradiation, identifying their damage thresholds. The employed hybrid code XTANT is capable of modeling both thermal and nonthermal effects under ultrafast electronic excitation. It allowed us to reveal common trends in the studied materials: all but the AlAs III-V compounds studied here exhibit a phase transition into a metallic disordered state of lower density than the solid phase via a thermal phase transition. This transition is instigated by electron-ion coupling at doses below the nonthermal melting. Irradiated AlAs showed two possible phases produced: low-density and high-density liquid. We demonstrate that the transferrable tight-binding method within the Born-Oppenheimer approximation significantly overestimates the damage threshold predicting only nonthermal melting in comparison to a non-Born-Oppenheimer scheme, which accounts for both effects and their interplay.

Effect of WET treatment on Group III-V Compound Semiconductor Surface

In this work, we investigated interfacial properties of InP, which is a typical group III-V compound used for semiconductors, by using a chemical-treated metal oxide semiconductor (MOS) capacitor. The interfacial properties of InP is more affected by interface state density than the surface roughness and is greatly affected by In2O3in particular. Additionally, we evaluated In2O3growth during 24-hour rinsing and air exposure and found that In2O3on an InP surface grows larger during rinsing than during air exposure. To reduce In2O3, the rinse needs to be optimized.

(Invited) Novel Luminescent Materials Based on Semiconductor Nanowires

We report novel luminescent materials based on group III-V compound semiconductor nanowires. Semiconductor nanowires are essentially one-dimensional rods with length of several microns and diameter below 100 nm. Hence, nanowires exhibit interesting quantum confinement and carrier transport properties. Nanowires are grown using metal seed particles by the vapor-liquid-solid (VLS) process in a molecular beam epitaxy or metalorganic chemical vapor deposition system. By varying the material deposition during growth, axial or radial nanowire heterostructures and p-n junctions may be formed for various device applications including light emitting diodes, lasers, and photodetectors. Due to the large surface area to volume ratio of a nanowire, lattice mismatch strain may be accommodated by elastic distortion of the nanowire without detrimental misfit dislocations, which gives a much greater ability to perform bandgap engineering in nanowires as compared to thin films. Hence, unique heterostructures are possible in nanowires that would be impossible in thin films, opening up new device applications and possibilities in condensed matter physics. We will report our recent work on the photoluminescence properties of InAsP/InP nanowires. InP nanowires were grown on <111> Si substrates by the Au-assisted vapor-liquid-solid process in a gas source molecular beam epitaxy system. InAsyP1-y segments were grown in the middle of the InP nanowires, creating a multiple quantum dot structure or superlattice. The quantum dot dimensions and composition were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDX). Photoluminescence (PL) from the quantum dot structure could be tuned by the InAsyP1-y composition (y), or by the size of the quantum dot via the quantum confinement effect. Cathodoluminescence (CL) measurements confirmed localized emission from the quantum dots. To reduce detrimental surface states, the nanowires were passivated with an AlInP shell, which resulted in strong PL emission.The growth mechanism of the quantum dots were inferred from the InAsP and InP segment lengths as a function of nanowire diameter. Short InAsP segment lengths were found to grow by depletion of In from the Au particle as well as by direct impingement, while longer segments of InAsP and InP grew by diffusive transport of adatoms from the nanowire sidewalls. The present study offers a manner to engineer the lengths of InAsP quantum dots embedded in InP barriers to better control the PL or CL emission. A novel group III and V gas switching sequence is presented to improve compositional control of the QD.

Low-power tunnel field effect transistors using mixed As and Sb based heterostructures

AbstractReducing supply voltage is a promising way to address the power dissipation in nano-electronic circuits. However, the fundamental lower limit of subthreshold slope (SS) within metal oxide semiconductor field effect transistors (MOSFETs) is a major obstacle to further scaling the operation voltage without degrading ON/OFF ratio in current integrated circuits. Tunnel field-effect transistors (TFETs) benefit from steep switching characteristics due to the quantum-mechanical tunneling injection of carriers from source to channel, rather than by conventional thermionic emission in MOSFETs. TFETs based on group III-V compound semiconductor materials further improve the ON-state current and reduce SS due to the low band gap energies and smaller carrier tunneling mass. The mixed arsenide/antimonide (As/Sb) InxGa1-xAs/GaAsySb1-y heterostructures allow a wide range of band gap energies and various staggered band alignments depending on the alloy compositions in the source and channel materials. Band alignments at source/channel heterointerface can be well modulated by carefully controlling the compositions of the mixed As/Sb material system. In particular, this review introduces and summarizes the progress in the development and optimization of low-power TFETs using mixed As/Sb based heterostructures including basic working principles, design considerations, material growth, interface engineering, material characterization, device fabrication, device performance investigation, band alignment determination, and high temperature reliability. A review of TFETs using mixed As/Sb based heterostructures shows superior structural properties and distinguished device performance, both of which indicate the mixed As/Sb staggered gap TFET as a promising option for high-performance, low-standby power, and energy-efficient logic circuit application.

Growth of Polycrystalline Indium Phosphide Nanowires on Copper

ABSTRACTOur nation discards more than 50% of the total input energy as waste heat in various industrial processes such as metal refining, heat engines, and cooling. If we could harness a small fraction of the waste heat through the use of thermoelectric (TE) devices while satisfying the economic demands of cost versus performance, then TE power generation could bring substantial positive impacts to our society in the forms of reduced carbon emissions and additional energy. To increase the unit-less figure of merit, ZT, single-crystal semiconductor nanowires have been extensively studied as a building block for advanced TE devices because of their predicted large reduction in thermal conductivity and large increase in power factor. In contrast, polycrystalline bulk semiconductors also indicate their potential in improving overall efficiency of thermal-to-electric conversion despite their large number of grain boundaries. To further our goal of developing practical and economical TE devices, we designed a material platform that combines nanowires and polycrystalline semiconductors which are integrated on a metallic surface. We will assess the potential of polycrystalline group III-V compound semiconductor nanowires grown on low-cost copper sheets that have ideal electrical/thermal properties for TE devices. We chose indium phosphide (InP) from group III-V compound semiconductors because of its inherent characteristics of having low surface states density in comparison to others, which is expected to be important for polycrystalline nanowires that contain numerous grain boundaries. Using metal organic chemical vapor deposition (MOCVD) polycrystalline InP nanowires were grown in three-dimensional networks in which electrical charges and heat travel under the influence of their characteristic scattering mechanisms over a distance much longer than the mean length of the constituent nanowires. We studied the growth mechanisms of polycrystalline InP nanowires on copper surfaces by analyzing their chemical, optical, and structural properties in comparison to those of single-crystal InP nanowires formed on single-crystal surfaces. We also assessed the potential of polycrystalline InP nanowires on copper surfaces as a TE material by modeling based on finite-element analysis to obtain physical insights of three-dimensional networks made of polycrystalline InP nanowires. Our discussion will focus on the synthesis of polycrystalline InP nanowires on copper surfaces and structural properties of the nanowires analyzed by transmission electron microscopy that provides insight into possible nucleation mechanisms, growth mechanisms, and the nature of grain boundaries of the nanowires.

Nanometre-scale electronics with III–V compound semiconductors

For 50 years the exponential rise in the power of electronics has been fuelled by an increase in the density of silicon complementary metal-oxide-semiconductor (CMOS) transistors and improvements to their logic performance. But silicon transistor scaling is now reaching its limits, threatening to end the microelectronics revolution. Attention is turning to a family of materials that is well placed to address this problem: group III-V compound semiconductors. The outstanding electron transport properties of these materials might be central to the development of the first nanometre-scale logic transistors.

Reflection Absorption Infrared Spectroscopy Study on the Spontaneous Formation of Erbium Monoantimonide Nanoparticles on Indium Antimonide Surfaces

ABSTRACTWe describe an ex-situ monitoring technique for a small amount (∼30 mono-layers) of erbium monoantimonide (ErSb) deposited on an indium antimonide (InSb) epitaxial layer prepared on InSb(100) substrates by metal organic chemical vapor deposition (MOCVD). Our objective is to improve thermoelectric properties of nanocomposites that employ nanometer size semi-metallic ErSb particles (ErSb nanoparticles) embedded in ternary group III-V compound semiconductor host materials such as indium gallium antimonide (InGaSb) and indium antimonide arsenide (InSbAs). The formation of ErSb nanoparticles embedded in a host material is spontaneous and needs to be carefully controlled to tune the size and volume density of the ErSb nanoparticles. We used an ex-situ monitoring technique based on glancing-angle infrared-absorption, reflection absorption infra-red spectroscopy (RAIRS), to study the formation of ErSb nanoparticles to correlate the amount of delivered ErSb and surface morphology of the surface of InSb covered with ErSb.

新素材：環境・エネルギー材料の新展開 ＩＩＩ‐Ｖ族混晶半導体の化学熱力学と結晶成長プロセス

The group III-V compound semiconductors and their solid solutions are important materials used in high speed electronic and optical electronic devices. Crystal growth of these semiconductor materials involves processes between the solid and liquid phases or solid and gas phase at near equilibrium conditions. Therefore, knowledge of thermodynamic and thermochemical properties for the semiconductor systems is important for providing optimum conditions in the analysis of processes for the crystal growth. In this report, some thermodynamic and thermochemical data such as heat capacity, standard entropy, heat and free energy of formation of compounds and heat of mixing of solid solutions on calorimetry are summarized. Base on these data, the vapor epitaxial growth of the III-V solid solution crystal are analyzed thermodynamically. The calculated compositions of the alloys have been compared with experiment, showing remarkably good agreement.

Oxide‐Assisted Growth of Semiconducting Nanowires

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electronic and optical properties of Ge-Si superlattices

Germanium and silicon elemental semiconductors are indirect bandgap, cubic materials that are used in the manufacture of the great majority of semiconductor electronic devices. Epitaxial techniques, largely borrowed and adapted from group III-V compound semiconductor technology, have been applied successfully to produce heterostructures and superlattices from Ge and Si. Theory shows that some of these structures behave like direct bandgap materials, while other structures can be used for optical second harmonic generation. On the other hand, it has been well understood for many years that neither silicon, nor germanium, nor any germanium-silicon alloy could ever show such behaviour. Recent progress in germanium-silicon heterostructures is reviewed in the context of developing a new materials system for photonic devices based entirely on silicon and germanium and suitable for optical waveguides, modulators, sources, and detectors.

Optimum semiconductors for high-power electronics

Elemental and compound semiconductors, including wide-bandgap semiconductors, are critically examined for high-power electronic applications in terms of several parameters. On the basis of an analysis applicable to a wide range of semiconducting materials and by using the available measured physical parameters, it is shown that wide-bandgap semiconductors such as SiC and diamond could offer significant advantages compared to either silicon or group III-V compound semiconductors for these applications. The analysis uses peak electric field strength at avalanche breakdown as a critical material parameter for evaluating the quality of a semiconducting material for high-power electronics. Theoretical calculations show improvement by orders of magnitude in the on-resistance, twentyfold improvement in the maximum frequency of operation, and potential for successful operation at temperatures beyond 600 degrees C for diamond high-power devices. New figures of merit for power-handling capability that emphasize electrical and thermal conductivities of the material are derived and are applied to various semiconducting materials. It is shown that an improvement in power-handling capabilities of semiconductor devices by three orders of magnitude is feasible by replacing silicon with silicon carbide; improvement in power-handling capability by six orders of magnitude is projected for diamond-based devices. >

Properties of low-temperature (80-300° C) pyrolytic SiO2 on Si and InP

We report on a new low-temperature pyrolytic deposition technology for silicon dioxide. We present data characterizing the electrical and optical properties of this dielectric deposited on Si and InP substrates. The effects of thermal processing are also reported. Deposition of high-quality SiO2 is achieved by reacting SiH4 and O2 at pressures of 2–12 Torr. Reactions occur by pyrolysis only, promoting stoichiometric SiO2 deposition and good interfacial properties. No plasma- or photo-enhancement is required. Deposition is achieved at temperatures as low as 80° C, the lowest temperature ever reported for pyrolytic SiO2 deposition. Rates as high as 65 A/min at 100° C and 100-150 A/min at 150-300° C are attained. The leakage current densities measured for both Si and InP MIS capacitors (e.g. 10-9 A/cm2 for 150° C SiO2) are two to six orders of magnitude lower than values reported for plasma- and photo-enhanced SiO2 deposited at equivalent temperatures. The high-temperature integrity of this dielectric also makes it a promising annealing cap for group III-V compound semiconductors. Our annealing studies show that SiO2-capped indium phosphide surfaces remain specular up to 850° C.

Safety in thin film semiconductor deposition

Special safety precautions are required in thin film photovoltaics manufacture because of the hazardous nature of the source gases used for deposition. Most of these gases are pyrophoric or flammable and dangerously unstable in air but it is the toxicity of some that causes the greatest concern. Therefore the issue addressed here is the control of toxic airborne substances to minimize the hazards associated with their use. Safety considerations are discussed with specific reference to the chemical vapor deposition of silicon from the chlorosilanes, the chemical vapor deposition of group III-V compound semiconductors using the metalorganic-hydride chemistry and the plasma deposition of amorphous silicon and silicon-germanium alloys using silane and germane.

極微小域材料分析の最近の進歩 種々の材料への応用 エレクトロニクス材料（ＩＩＩ‐Ｖ族化合物半導体デバイス開発への応用）

極微小域材料分析の最近の進歩 種々の材料への応用 エレクトロニクス材料（ＩＩＩ‐Ｖ族化合物半導体デバイス開発への応用）