Type InP Research Articles

Electronic and optical properties of Zn-doped InGaAs emission layer with vacancy defects: A DFT study

In0.53Ga0.47As is an important material for the shortwave near-infrared negative electron affinity photocathodes. Zn atoms were doped in the intrinsic InGaAs to form p-type In0.53Ga0.44 Zn0.03As emission layer. Models of Zn-doped In0.53Ga0.44 Zn0.03As bulk with In, Ga or As vacancy defect were built in the article. Emphasis was put on how the defects influence the microstructure and the optical properties of the Zn-doped InGaAs emission layer. Combined effect of both vacancy defects and doped Zn atoms for the photoelectron emission performance was further studied. It is indicated that the In or Ga vacancy defect is easier to be generated than the As from the analysis of formation energy. However, As vacancy defect is more benefit for photoelectrons emission considering the material polarity because As vacancy defect interacting with doped Zn atoms is a positive center and generates acceptor level to narrow the energy gap. At the same time Zn ion will be easier to accept electrons when the As vacancy defect appears. The absorption coefficient of the InGaAs emission layer with As vacancy defect is also bigger than that with In or Ga defect. In conclusion, As vacancy defect is benefit and will promote the photoemission of InGaAs photocathode while the In or Ga vacancy defect should be avoided when the emission layer is grown.

Inversion in the In0.53Ga0.47As metal-oxide-semiconductor system: Impact of the In0.53Ga0.47As doping concentration

In0.53Ga0.47As metal-oxide-semiconductor (MOS) capacitors with an Al2O3 gate oxide and a range of n and p-type In0.53Ga0.47As epitaxial concentrations were examined. Multi-frequency capacitance-voltage and conductance-voltage characterization exhibited minority carrier responses consistent with surface inversion. The measured minimum capacitance at high frequency (1 MHz) was in excellent agreement with the theoretical minimum capacitance calculated assuming an inverted surface. Minority carrier generation lifetimes, τg, extracted from experimentally measured transition frequencies, ωm, using physics based a.c. simulations, demonstrated a reduction in τg with increasing epitaxial doping concentration. The frequency scaled conductance, G/ω, in strong inversion allowed the estimation of accurate Cox values for these MOS devices.

Effect Of Phases On The Energetics Of Pristine InP Nanowires: An Ab-initio Approach

We have investigated the electronic and structural properties of pristine Zinc-blende type InP nanowires (NWs) by using ab-initio approach. We have considered the effect of phases by taking NWs of 7 A radii in three phases viz. (100), (110), (111). It is revealed that the electronic properties of NWs are highly affected by the wire phases. NW in (100) phase is found to be semiconducting with an indirect band gap of 0.71 eV whereas it becomes semi-metallic and metallic in other two phases. Thus, the nature of nanowires is observed as a function of NW phases. Further, energetic feasibility of InP NWs strongly dependent on their growth phase. Copyright © 2016 VBRI Press.

THE CHARACTERISTIC DIODE PARAMETERS IN Ti/p-InP CONTACTS PREPARED BY DC SPUTTERING AND EVAPORATION PROCESSES OVER A WIDE MEASUREMENT TEMPERATURE

The titanium/[Formula: see text]-indium phosphide (Ti/[Formula: see text]-InP) Schottky diodes (SDs) have been prepared by thermal evaporation and DC magnetron sputtering deposition. Then, their current–voltage ([Formula: see text]–[Formula: see text]) characteristics have been measured in the sample temperature range of 100–400[Formula: see text]K with steps of 20[Formula: see text]K. The characteristic parameters of both Ti/[Formula: see text]-InP SDs have been compared with each other. The barrier height (BH) values of 0.824 and 0.847 at 300[Formula: see text]K have been obtained for the sputtered and the evaporated SDs, respectively. This low BH value for the sputtered SD has been attributed to some defects introduced by the sputtered deposition technique over a limited depth in to the [Formula: see text]-type substrate. The BH of the evaporated and sputtered diodes has decreased with the standard deviations of 58 and 64[Formula: see text]mV obeying to double-Gaussian distribution (GD) in 220–400[Formula: see text]K range, respectively, and it has seen a more sharper reduction for the BHs with the standard deviations of 93 and 106 mV in 100–220[Formula: see text]K range. The Richardson constant values of 89.72 and 53.24[Formula: see text]A(Kcm)[Formula: see text] (in 220–400[Formula: see text]K range) for the evaporated and sputtered samples, respectively, were calculated from the modified ln([Formula: see text]/[Formula: see text]/2[Formula: see text] vs (kT)[Formula: see text] curves by GD of the BHs. The value 53.24[Formula: see text]A(Kcm)[Formula: see text] for the sputtered sample in high temperatures range is almost the same as the known Richardson constant value of 60[Formula: see text]A(Kcm)[Formula: see text] for [Formula: see text]-type InP.

Short-wavelength infrared array avalanche photodetectors on the basis of InGaAs heteroepitaxial structures

SWIR ADP 320 × 256 FPAs based on p–i–n photodiodes in InGaAs heterostructures have been developed and investigated. The typical InGaAs/InP PIN heterostructures are formed by Metal Organic Vapor Phase Epitaxy (MOVPE) on n+ type InP substrates. The InGaAs/InP PIN photodiodes performance have been estimated by measuring current-voltage characteristics. APD arrays are designed using a mesa-passivated avalanche photodiode device array of p–i–n junctions in heterostructure with common absorption and multiplication regions. The optimal operating point for managing avalanche application depended on various factors has been started at 15 V bias and the multiplication coefficient was of 2–4.

Effect of forming gas annealing on the inversion response and minority carrier generation lifetime of n and p-In0.53Ga0.47As MOS capacitors

In0.53Ga0.47As MOS capacitors with a range of Al2O3 oxide thickness values were examined using multi-frequency capacitance–voltage and conductance–voltage characterization for n and p-type In0.53Ga0.47As epitaxial layers. The samples exhibited a minority carrier response consistent with surface inversion for both n and p-type In0.53Ga0.47As MOS structures. An equality between the peak magnitude of the frequency scaled conductance, G/ω, and the derivative of capacitance with frequency, −ωdC/dω in strong inversion allows estimation of accurate Cox values for the varying thickness MOS devices. Minority carrier generation lifetimes, τg, were extracted from the experimentally measured transition frequencies, ωm, through physics based a.c. simulations. It was observed that τg was reduced following a post-metallization 275°C forming gas anneal treatment over both n and p-In0.53Ga0.47As. This is indicative of an improvement in the In0.53Ga0.47As quality by means of hydrogen passivation of the mid-gap bulk defects responsible for the observed minority carrier response.

Power-Generation Characteristics After Vibration and Thermal Stresses of Thermoelectric Unicouples with CoSb3/Ti/Mo(Cu) Interfaces

Reliability tests for thermoelectric unicouples were carried out to investigate the adhesion properties of CoSb3/Ti/Mo(Cu) interfaces. The n-type In0.25 Co3.95Ni0.05Sb12 and p-type In0.25Co3FeSb12 bulks were prepared for fabricating a thermoelectric unicouple (one p–n couple) by an induction melting and a spark plasma sintering process. Mo-Cu alloy was selected as an electrode for the unicouples due to its high melting temperature and proper work function value. Many thermoelectric unicouples with the CoSb3/Ti/Mo(Cu) interfaces were fabricated with the proper brazing materials by means of a repeated firing process. Reliability of the unicouples with the interfaces was evaluated by a vibration test and a thermal cycling test. After the thermal cycling and vibration tests, the power-generation characteristics of the unicouples were compared with the unicouples before the tests. Even after the vibration test, electrical power with a power density of 0.5 W/cm2 was generated. The Ti-interlayer is considered as a possible candidate for making a reliable unicouple with high adhesion strength. With the thermal cycling test, the resistance of the unicouple increased and the electrical power from the unicouple decreased. A failure mode by the thermal cycling test was ascribed to a complex effect of micro-cracks originated from the thermal stress and oxidation problem of the thermoelectric materials; that is, a thick oxide layer more than 300 μm was detected after a high-temperature durability test of n-type In0.25Co3.95Ni0.05Sb12 material at 773 K in air for 7 days.

Raman scattering study of LO phonon–plasmon coupled modes in p-type InGaAs

We present a Raman scattering study of LO phonon-coupled modes in Be-doped, p-type In0.53Ga0.47As with hole densities ranging from 2.2×1017 to 2.4×1019cm−3. Two separate phonon-like coupled modes are observed in the optical-phonon spectral region, corresponding to InAs-like and GaAs-like overdamped modes. With increasing free-hole density, these modes exhibit a redshift and their frequencies approach the respective TO frequencies. Unlike the case of n-type material, no high-frequency L+ coupled mode could be detected. The Raman spectra are analyzed using a dielectric model based on the Lindhard–Mermin susceptibility that takes into account HH and LH intraband transitions as well as HH–LH interband transitions. The model yields good quality fits to the experimental spectra. It is shown that the inter-valence-band processes introduces an additional damping channel that causes the L+ mode to be damped out. The comparison between the Raman spectra and the theoretical line-shape calculations suggests the presence of a residual strain and a reduced sublattice interaction in the most heavily doped samples.

Influence of Annealing and Sintering on the Thermoelectric and Mechanical Properties of Gas Atomized p-type Skutterudites

Filled cobalt-antimony based skutterudites are very promising thermoelectric materials for generator applications in an intermediate temperature range between 150 and 550°C. For applications, besides the functional thermoelectric properties also the mechanical properties and production methodsplay an important role. Both thermoelectric and mechanical properties can be varied by adjusting the doping level, filling elements and filling fraction. Furthermore, the properties can be influenced by the choice of preparation routes leading to the formation of certain nano- or microstructures.In this work we investigate the influence of powder treatment and sintering temperature on the properties of p-type In0.2Fe0.28Co3.72Sb12 skutterudites synthesized by gas atomization. After atomization the powder contains a large fraction of secondary phases which transform into the skutterudites phase during short term sintering. This phase transformation supports compaction and sintering. It is shown that the sintering temperature influences the resulting thermoelectric properties beyond pure effects of porosity. Best thermoelectric material propertiesare achieved at sintering temperatures between 550 and 600°C. Annealing the atomized powder prior to sintering leads to phase pure material for which the sintering temperature only influences the thermoelectric properties via the resulting sample porosity.

(Invited) Passivation of Al2O3/n, p-In0.53Ga0.47 as Interfaces: Influence of Plasma Enhanced Atomic Layer Deposition Aluminum Nitride with Various Plasma Powers

Plasma enhanced atomic layer deposition (PEALD) aluminum nitride (AlN) is attracting great interests as an advanced technique for high-k/III-V interfacial passivation. In this study, we demonstrate the effects of PEALD-AlN layer deposition plasma powers on the electrical properties of both n-type and p-type In0.53Ga0.47As based metal oxide semiconductor capacitors (MOSCAPs). By using PEALD-AlN as interfacial passivation layer (IPL) at the Al2O3/n, p-In0.53Ga0.47As interface, noticeable enhancement of electrical characteristics including small capacitance-voltage (C-V) hysteresis, small frequency dispersion values, and low interface state densities (Dit) have been observed. After performing 5 cycles of PEALD-AlN IPL at optimized plasma power of 150 W, multifrequency C-V responses exhibit excellent behaviors for both n-type and p-type Al2O3/AlN/In0.53Ga0.47As MOSCAPs. The Dit values are extracted to be 5.3 × 1011 – 1.2 × 1012 cm-2 eV-1 and 1.6 × 1011 - 2.7 × 1011 cm-2 eV-1 at the trap energy level of 0.47 – 0.4 eV and 0.2 – 0.26 eV above the edge of valence band (EV) for n-type and p-type MOSCAPs, respectively. X-ray photoelectron spectroscopy (XPS) analysis reveals that the enhancement of Dit values cannot be fully explained by the reduction of native oxides at the InGaAs surfaces. The original reason of interface defects states is attributed to the surface dangling bonds that were passivated by the polycrystalline PEALD-AlN passivation layer as illustrated in the high resolution transmission electron microscopy (HRTEM) image.

The Characterization and Passivation of Fixed Oxide Charges and Interface States in the $\hbox{Al}_{2}\hbox{O}_{3}/ \hbox{InGaAs}$ MOS System

In this paper, we present a review of experimental results examining charged defect components in the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As metal-oxide-semiconductor (MOS) system. For the analysis of fixed oxide charge and interface state density, an approach is described where the flatband voltage for n- and p-type Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As MOS structures is used to separate and quantify the contributions of fixed oxide charge and interface state density. Based on an Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thickness series (10-20 nm) for the n- and p-type In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As layers, the analysis reveals a positive fixed charge density ( ~ 9 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ) distributed throughout the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and a negative sheet charge density (- 8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ) located near the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As interface. The interface state density integrated across the energy gap is ~1 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> and is a donor-type (+/0) defect. The density of the fixed oxide charge components is significantly reduced by forming gas (5 % H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> / 95% N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambient at 350 °C for 30 minutes) annealing. The interface state distribution obtained from multi-frequency capacitance-voltage and conductance-voltage measurements on either MOS structures or MOSFETs indicates a peak density located around the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As midgap energy, with a sharp increase in the interface state density toward the valance band and evidence of interface states aligned with the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As conduction band. The integrated interface state density obtained from multi-frequency capacitance-voltage and conductance-voltage analysis is in good agreement with the approach of comparing the flatband voltages in n- and p -type Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As MOS structures. Finally, this paper reviews recent work based on an optimization of the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As surface preparation using (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S, combined with minimizing the transfer time to the atomic layer deposition reactor for Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , which indicates interface state reduction and genuine surface inversion for both n- and p -type Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.53</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.47</sub> As MOS structures.

Lower limits to metal-semiconductor contact resistance: Theoretical models and experimental data

We calculate the minimum feasible contact resistivity to n-type and p-type In0.53Ga0.47As, InAs, GaAs, GaSb, InP, and InSb. The calculations consider image force lowering and assume either parabolic or non-parabolic energy dispersion in the semiconductor; their results are compared with recent experimental data. Among significant results, the measured contact resistivity to n-In0.53Ga0.47As at a carrier concentration of 5 × 1019 cm−3 is only 2.3:1 higher than that calculated assuming a 0.2 eV barrier potential, and the measured contact resistivity is only 9.0:1 larger than the Landauer quantum conductivity limit at this carrier concentration. These results indicate that, with the surface preparation procedures presently employed, surface contamination does not markedly increase the interface resistance, and that the transmission coefficient for carriers crossing the interface exceeds 10%.

Broadband InGaAs quantum dot-in-a-well solar cells of p-type wells

Broadband InxGa1−xAs quantum dot-in-a-well (DWell) solar cells are grown by stacking layers of composition-tailored InxGa1−xAs (x=1, 0.75, and 0.65) quantum dots on p-type In0.1Ga0.9As quantum wells (QWs). Doping concentration and growth temperature for the Be-doped quantum wells are optimized to enhance the conversion efficiency (η). The broadband DWell solar cell of Be: 2×1017cm−3 QWs grown at 570°C shows the best photovoltaic characteristics of η=10.86%, which is 3% higher than that of the GaAs baseline solar cell.

CoInGaAs as a novel self-aligned metallic source/drain material for implant-less In0.53Ga0.47As n-MOSFETs

CoInGaAs, a new self-aligned silicide-like source/drain (S/D) metallic contact, was demonstrated on In0.53Ga0.47As n-MOSFET. Co reacts with In0.53Ga0.47As at temperatures as low as 350°C, forming metallic material comprising regions rich in cobalt gallium and cobalt arsenide. The CoInGaAs formed exhibits Schottky characteristic on p-type In0.53Ga0.47As, and is thus suitable for S/D material. It also exhibits ohmic behavior on n-type In0.53Ga0.47As (doping concentration of ∼5×1019cm−3) with contact resistance and specific contact resistivity of ∼1.12kΩμm and ∼6.25×10−4Ωcm2, respectively. The integration of CoInGaAs as metallic S/D material in In0.53Ga0.47As n-MOSFET produces reasonably well-behaved output characteristics.

On the activation of implanted silicon ions in p-In0.53Ga0.47As

We present a systematic study of Si dopant implantation and activation in p-type In0.53Ga0.47As in an attempt to optimize the source and drain regions of an n-channel III-V metal–oxide–semiconductor field-effect transistor. Test structures based on the transfer length method were fabricated on Si-implanted p-In0.53Ga0.47As/p-InP buffer/semi-insulting InP. A Doehlert design of experiment (DOE) was used to investigate the effect of annealing temperature and time on the electrical properties of the samples. The DOE covered an experimental domain of 625–725 °C and 15–45 s. The current–voltage characteristics of all tested structures exhibited excellent ohmic behavior. The DOE revealed a minimum sheet resistance of (195.6 ± 3.4) Ω/□ for an optimum anneal condition of 715 °C for 32 s. Nonalloyed Au/Ge/Au/Ni/Au contacts, on the sample annealed at 675 °C for 30 s (center point of the experimental domain), exhibited a low specific contact resistance of (7.4 ± 4.5) × 10−7 Ω cm2. The sample annealed at 675 °C for 30 s was further investigated using secondary ion mass spectrometry (SIMS) and cross-sectional transmission electron microscopy (XTEM) analyses. SIMS revealed that Si ions did not diffuse with annealing, while XTEM showed the formation of characteristic loop defects potentially responsible for the sheet resistance and specific contact resistance degradation.

Effect of annealing ambient and temperature on the electrical characteristics of atomic layer deposition Al2O3/In0.53Ga0.47As metal-oxide-semiconductor capacitors and MOSFETs

In this work, we investigate the effect of forming gas annealing (FGA) on n-type and p-type In0.53Ga0.47As MOS capacitors with atomic layer deposition (ALD) Al2O3 high-κ dielectric. The as-deposited samples have a significant amount of fixed charge in the bulk of the gate dielectric and at the dielectric/semiconductor interface, which causes the flatband voltage (VFB) to have an oxide thickness dependent shift. Through FGA, we successfully (1) reduce the amount of bulk and interface fixed charge in the Al2O3, and (2) improve the Al2O3/InGaAs interface. The reduction in fixed charge is verified through an alignment of the VFB across all dielectric thicknesses. The gate stack improvement is qualitatively illustrated through a sharper capacitance-voltage (C-V) curve and quantitatively verified through a reduction of the interface trap density (DIT). The effect of the annealing temperature (300–400 °C) and ambient (N2 and forming gas (FG)) are investigated in detail through electrical characterization by C-V, I-V, DIT, fixed charge density (QF), and interface sheet charge (QIT) measurements. We find that there exists a trade-off where higher annealing temperatures result in a lower DIT, but comes at the cost of higher gate leakage. Furthermore, by comparing the effect of annealing in inert N2 versus FG, we are able to distinguish the effect of hydrogen in the FGA from the purely thermal effects of annealing. We discover that hydrogen passivation of dangling bonds and border traps is responsible for improving the interfacial properties, while the thermal budget is responsible for minimizing the fixed charge. Finally, we study the benefit of FGA on InGaAs nMOSFET device performance and demonstrate that the on-current increases by 25% after annealing at 350 °C for 30 min. A thorough understanding of the impact of FGA is crucial for threshold voltage tuning and improvement of the InGaAs MOSFET gate stack.

A Resistance Ratio Analysis for CoSb3-Based Thermoelectric Unicouples

In the search for desirable materials for use in thermoelectric generators, CoSb3-based skutterudites have stimulated much scientific interest due to their high performance capabilities even at high temperatures. In this work, we tested the electrical power-generation characteristics of CoSb3-based unicouples. We manufactured power-generation unicouples using n-type In0.25Co3.95Ni0.05Sb12 and p-type In0.25Co3.0Fe1.0Sb12 legs. The dimensions of the thermoelectric legs were 10 mm in diameter and 10 mm in height, with Cu sheets and Cu/Mo alloy as the electrode materials. For our unicouples, we evaluated the resistance ratio m′ (=Ro/R), which represents the ratio of the load resistance to the internal resistance of the unicouple. From this analysis of the resistance ratio m′, we obtained a considerable amount of information about the loss factors that caused the difference between the measured power output and the theoretical value. Through these analyses of two types of loss factors, we sought to improve the open-circuit voltage and internal resistance of a unicouple with CoSb3/Ti/electrode interfaces. In addition, a long-term durability test of the unicouple at high temperature was performed to test the stability of the thermoelectric materials and of the interface between the electrodes and the thermoelectric legs at the same time.

Analysis of the minority carrier response of n-type and p-type Au/Ni/Al2O3/In0.53Ga0.47As/InP capacitors following an optimized (NH4)2S treatment

The electrical properties of metal-oxide-semiconductor capacitors incorporating atomic layer deposited Al2O3 on n-type and p-type In0.53Ga0.47As were investigated. A clear minority carrier response was observed for both n-type and p-type Au/Ni/Al2O3/In0.53Ga0.47As devices following an optimized ammonium sulfide (NH4)2S treatment. Capacitance-voltage and conductance-voltage measurements performed at varying temperatures allowed an Arrhenius extraction of activation energies for the minority carrier response, indicating a transition from a generation-recombination regime to a diffusion controlled response.

Photoelectron spectroscopy study of band alignment at interface between Ni-InGaAs and In0.53Ga0.47As

The work function of Ni-InGaAs and the band alignment between Ni-InGaAs and In0.53Ga0.47As were investigated using photoelectron spectroscopy. The vacuum work function of Ni-InGaAs is obtained to be ∼5.1 eV using ultraviolet photoelectron spectroscopy (UPS). In addition, it was observed that the Fermi level of Ni-InGaAs is aligned to near conduction band of In0.53Ga0.47As at interface. For Ni-InGaAs formed on p-type In0.53Ga0.47As, this gives a Schottky contact with a hole barrier height of 0.8 ± 0.1 eV. Ni-InGaAs would form an ohmic contact on n-type In0.53Ga0.47As.

Schottky-barrier height modulation of metal/In0.53Ga0.47As interfaces by insertion of atomic-layer deposited ultrathin Al2O3

The improvement of the metal/InGaAs interface is essential for the future application of InGaAs metal source/drain Schottky-barrier metal-oxide-semiconductor field-effect-transistors. In this article, on In0.53Ga0.47As, the authors examine the recently proposed method of inserting an ultrathin insulator to modulate the effective Schottky-barrier height (SBH) at the metal/semiconductor interface. Both n-type and p-type In0.53Ga0.47As are investigated by inserting an atomic-layer deposited Al2O3 interlayer. The results indicate that SBH modulation is more effective at the n-InGaAs interface than the p-InGaAs interface for the same Al2O3 thickness. However, the Fermi level at the metal/InGaAs interface is still weakly pinned even after inserting 2 nm Al2O3. The mechanism of the SBH modulation could be attributed to the creation of an electric dipole at the Al2O3/InGaAs interface, which induces a barrier shift.