Modification of the parameters of thermal converter branches based on bismuth and antimony chalcogenides by means of copper intercalation

The phenomenon of conductivity type conversion (p → n) upon copper intercalation into layered crystals of bismuth and antimony chalcogenides has been used to create a thermal converter cell proceeding from the initial p-type chalcogenide crystals. The necessary n-type conductivity branches were formed upon assembly of the cell by saturating the material with copper using the method of autoelectrochemical doping (AED). The possibility of using the AED method for the optimization of characteristics of the n-and p-type branches of thermal converters by means of copper introduction in small amounts into the materials is considered.     

Determination of the laterally homogeneous barrier height of metal/p-InP Schottky barrier diodes

We have reported a study of a number of metal/p-type InP (Cu, Au, Al, Sn, Pb, Ti, Zn) Schottky barrier diodes (SBDs). Each one diode has been identically prepared on p-InP under vacuum conditions with metal deposition. In Schottky diodes, the current transport occurs by thermionic emission over the Schottky barrier. The current–voltage characteristics of Schottky contacts are described by two fitting parameters such as effective barrier height and the ideality factor. Due to lateral inhomogeneities of the barrier height, both characteristic diode parameters differ from one diode to another. We have determined the lateral homogeneous barrier height of the SBDs from the linear relationship between experimental barrier heights and ideality factors that can be explained by lateral inhomogeneity of the barrier height. Furthermore, the barrier heights of metal–semiconductor contacts have been explained by the continuum of metal-induced gap states (MIGS). It has been seen that the laterally homogeneous barrier heights obtained from the experimental data of the metal/p-type InP Schottky contacts quantitatively confirm the predictions of the combination of the physical MIGS and the chemical electronegativity.     

Hybrid p-type ZnO film and n-type ZnO nanorod p-n homo-junction for efficient photovoltaic applications

Simple hybrid p-n homo-junctions using p-type ZnO thin films and n-type nanorods grown on fluorine tin oxide (FTO) substrates for photovoltaic applications are described. The ZnO nanorods (1.5 μm) were synthesized via an aqueous solution method with zinc nitrate hexahydrate and hexamethylenetetramine on ZnO seed layers. The 10-nm-thick ZnO seed layers showed n-type conductivity on FTO substrates and were deposited with a sputtering-based method. After synthesizing ZnO nanorods, aluminum-nitride co-doped p-type ZnO films (200 nm) were efficiently grown using pre-activated nitrogen (N) plasma sources with an inductively-coupled dual-target co-sputtering system. The structural and electrical properties of hybrid p-n homo-junctions were investigated by scanning electron microscopy, transmittance spectrophotometry, and I-V measurements.     

Anisotropic thermoelectric properties of the layered compounds PbSb<Subscript>2</Subscript>Te<Subscript>4</Subscript> and PbBi<Subscript>4</Subscript>Te<Subscript>7</Subscript>

Single crystals of the ternary layered compounds PbSb₂Te₄ (p-type) and PbBi₄Te₇ (n-type) have been grown by Czochralski pulling with melt supply through a floating crucible. The in-plane and out-of-plane thermoelectric power, electrical conductivity, and thermal conductivity of the PbSb₂Te₄ and PbBi₄Te₇ crystals and related alloys have been measured in the temperature range 85–340 K. The results attest to a significant thermoelectric anisotropy in the crystals, especially in the p-type material PbSb₂Te₄.     

Properties of CdSe single crystals activated with selenium by ion implantation

Selenium ion implantation has been used to produce p-type layers on cadmium selenide single crystals. Their conductivity is governed by acceptor levels at E _ν + 0.05 eV and E _ν + 0.32 eV, due to native point defects in the ion-implanted layer.     

Photoelectrochemical solar cell fabrication with tungsten diselenide single crystals

Recent reports on highly efficient photoelectrochemical solar cells withn-type WSe₂ have prompted us to grown-type single crystals of WSe₂ using a chemical vapour transport method. Different transporting agents have been used. It is seen that SeCl₄ transporter leads to very large single crystals ofp-type WSe₂, whereas the same transporting agent with excess amount of Se leads ton-type single crystals. PEC solar cells fabricated withp-type andn-type crystals thus grown have been reported and the results discussed.     

LPE InP layers grown in the presence of rare-earth elements

Preparation and characterisation of InP layers grown by Liquid Phase Epitaxy with the addition of several rare-earth (RE) elements into the growth melt is reported and the influence of Ho, Er, Nd Pr, and Yb is compared. Low-temperature photoluminescence (PL) spectra have been measured for various levels of excitation power and temperature. The major manifestation of the RE admixture is the pronounced narrowing of PL curves and the corresponding appearence of fine spectral features. Particularly in the case of Nd and Pr admixtures the acceptor related PL band exhibits a structure that permits an individual determination of acceptor and donor binding energies. Temperature dependent Hall effect and capacitance–voltage curves also show quite dramatic impact of Pr and Nd on shallow impurity and free-carrier concentrations: they were reduced by as much as three orders of magnitude.     

Determination of the laterally homogeneous barrier height of metal/p-InP Schottky barrier diodes

We have reported a study of a number of metal/p-type InP (Cu, Au, Al, Sn, Pb, Ti, Zn) Schottky barrier diodes (SBDs). Each one diode has been identically prepared on p-InP under vacuum conditions with metal deposition. In Schottky diodes, the current transport occurs by thermionic emission over the Schottky barrier. The current–voltage characteristics of Schottky contacts are described by two fitting parameters such as effective barrier height and the ideality factor. Due to lateral inhomogeneities of the barrier height, both characteristic diode parameters differ from one diode to another. We have determined the lateral homogeneous barrier height of the SBDs from the linear relationship between experimental barrier heights and ideality factors that can be explained by lateral inhomogeneity of the barrier height. Furthermore, the barrier heights of metal–semiconductor contacts have been explained by the continuum of metal-induced gap states (MIGS). It has been seen that the laterally homogeneous barrier heights obtained from the experimental data of the metal/p-type InP Schottky contacts quantitatively confirm the predictions of the combination of the physical MIGS and the chemical electronegativity.     

Stable p-type ZnO films grown by atomic layer deposition on GaAs substrates and treated by post-deposition rapid thermal annealing

Long-term stable p-type ZnO films were grown by atomic layer deposition on semi-insulating GaAs substrates and followed by rapid thermal annealing (RTA) in oxygen ambient. Significant decrease in the electron concentration and increase in the hole concentration, together with the intensity enhancement of acceptor-related A^oX spectral peak and the shift of bound exciton peak from D^oX to A^oX in the low-temperature photoluminescence spectra, were observed as the RTA temperature increased. Conversion of conductivity from intrinsic n-type to extrinsic p-type ZnO occurred at the RTA temperature of 600 °C. The p-type ZnO film with a hole concentration as high as 3.44 × 10²⁰ cm^− 3 and long-term stability up to 180 days was obtained as the RTA treatment was carried out at 700 °C. The results were attributed to the diffusion of arsenic atoms from GaAs into ZnO as well as the activation of As-related acceptors by the post-RTA treatment.     

P-type InP grown by liquid phase epitaxy with rare earths: not intentional Ge acceptor doping

InP single crystal layers were grown by liquid phase epitaxy (LPE) on semi-insulating InP:Fe substrates with praseodymium added to the melt. Room temperature Hall effect measurements revealed p-type conductivity of the layers with the hole concentration 6×10¹⁴ cm⁻³ and mobility 150 cm² V⁻¹ s⁻¹. By measuring temperature dependence of the hole concentration the binding energy of the dominant acceptor was determined as 223 meV. A photoluminescence line was found at 1.195 eV, close to the previously estimated no-phonon line of Ge acceptor transitions in Ge doped n-type InP. It was concluded that Ge acceptors cause the p-type conductivity of the grown layers.     

Crystal-chemical models of the defect system in nonstoichiometric and oxygen-doped ZnSe crystals

Quasi-crystal-chemical formulas that take into account the generation of point defects and defect complexes have been proposed for nonstoichiometric, self-doped, and oxygen-doped n- and p-type ZnSe crystals. The defect densities and electron, hole, and Hall carrier concentrations have been evaluated as functions of nonstoichiometry and dopant (Zn, Se, and O) concentration, and conditions have been identified for producing zinc selenide with a given conductivity type and tailored carrier concentration.     

The Influence of Heat Treatment on the Electrical Characteristics of Semi-Insulating SiC Layers Obtained by Irradiating <Emphasis Type="Italic">n</Emphasis>-SiC with High-Energy Argon Ions

Irradiation of crystalline n-type silicon carbide (n-SiC) with high-energy (53-MeV) argon ions was used to create near-surface semi-insulating (i-SiC) layers. The influence of subsequent heat treatment on the electrical characteristics of i-SiC layers has been studied. The most high-ohmic ion-irradiated i-SiC layers with room-temperature resistivity of no less than 1.6 × 10¹³ Ω cm were obtained upon the heat treatment at 600°C, whereas the resistivity of such layers heat-treated at 230°C was about 5 × 10⁷ Ω cm.     

Properties of Sn-doped Bi2Te3 − x Sex single crystals

The effect of Sn doping (0.2 and 0.4 at %) on the properties of Czochralski-grown single crystals of n-type Bi₂Te_2.85Se_0.15 solid solutions is studied. Thermoelectric power, electrical conductivity, thermal conductivity, and Hall effect measurements in the range 77–400 K demonstrate that Sn doping has a significant effect on the transport properties of the solid solutions. Between 300 and 370 K, the thermoelectric figure of merit of Bi_1.996Sn_0.004Te_2.85Se_0.15 single crystals is higher than that of the Sn-free solid solution. In addition, hot-microprobe thermoelectric power measurements, highly sensitive to variations in carrier concentration, indicate that the Sn-doped single crystals are very uniform in electrical properties, both along the growth direction and radially.     

Fabrication of <Emphasis Type="Italic">p</Emphasis>-type doped ZnO thin films using pulsed laser deposition

Two new methods were investigated for the fabrication of p-type doped ZnO thin films in a conventional pulsed laser deposition apparatus, but using only pure materials as targets. One of these is a sequential method and consists in firing alternatively the laser on a pure ZnO target and either a monocrystalline InP target (for phosphorus doping) or a Bi₂O₃ ceramic target (for bismuth doping). The other method consists in taking advantage of the lithium diffusion into a ZnO thin film while being deposited on a c-LiNbO₃ substrate at high temperature. Some structural and electronic properties of the ZnO material obtained using these methods were measured using secondary ion mass spectrometry, X-ray diffraction, laser photoluminescence and Hall apparatus respectively and compared with those obtained for pure n-type thin films. The main results of this study are as follows. The sequential deposition method was successful in incorporating InP in ZnO films but led to inhomogeneous In and P spatial distributions, while segregation of Bi₂O₃ within the ZnO was evidenced by both the X-ray diffraction and photoluminescence results. Electrical measurements have revealed n-type conductivity for the ZnO/InP and the ZnO/c-LiNbO₃ thin films and a peculiar behaviour for the ZnO/Bi₂O₃ samples which could point out to successful p-type doping for films containing smaller amounts of Bi₂O₃.     

The characteristics of sub-10 nm gate-length erbium-silicided n-type Schottky barrier metal-oxide-semiconductor field-effect-transistors

10 and 6 nm erbium-silicided n-type Schottky barrier metal-oxide-semiconductor field-effect transistors (SB-MOSFETs) were manufactured. The manufactured 10 nm n-type SB-MOSFET showed a large on/off current ratio (> 10⁶) with low leakage current less than 10^− 5 μA/μm due to the existence of the robust Schottky barrier between source and channel region. The saturation currents were 550 and 320 μA/μm when drain and gate voltages were 2 V and 3 V, for the 10 and 6 nm erbium-silicided n-type SB-MOSFETs, respectively. The manufactured SB-MOSFETs exhibited superior short channel characteristics due to the existence of Schottky barrier between source and channel region.     

Phase Transformation and Magnetostriction of (R-Pr)(Fe-T)_2 (R=Dy Tb; T=Co, Ni)

1. IntroductionMuch attention has been focused onmagnetostrictive materials RFe2, particularly,Tbo.zv~o.sDyo.vs~o.vFez (Terfenol-D), due to theirexcellellt magnetoelastic properties for the transducer deviceslll. Clark et al. firstly suggestedthat the pseudobinary compounds combined byTb, Dy and Fe could be constructed in an effortto reduce the anisotropy while maintaining largemagnetostrictionlZ]. Clark et al. also found in thecompensated system Tbl--.Pr.FeZ that (Tb, Pr)Fe3phase appea…     

Bulk growth of polycrystalline indium phosphide

The growth of polycrystalline indium phosphide of different grain sizes varying from 15μm to 4000μm has been discussed. The materials have been characterized by a variety of methods including electrical and optical techniques. Device application of the InP prepared was demonstrated by the fabrication of Ag Schottky diodes andp ⁺-n junction using Zn diffusion. The variation of mobility with varying grain size has been determined experimentally and the results interpreted taking into account the effect of compensation.     

The recent advances of research on p-type ZnO thin film

ZnO is a direct wide-band gap (3.37 eV) compound semiconductor with large exciton binding energy (60 meV) at room temperature. Therefore it has a strong potential for various short-wavelength optoelectronic device, and now attracts tremendous renew interests for developing highly efficient ZnO-based optoelectronic devices. While high quality ZnO p–n junction materials obtained is the key step of its optoelectronic application. Whereas ZnO thin film is naturally only n-type conductivity due to a large number of native defects, such as oxygen vacancies and zinc interstitials, which lead to difficulty in achieving p-type ZnO thin film. Therefore the fabrication of p-type ZnO thin film has been a key and hotspot of the research on ZnO. This article summarizes the recent advances of the studies on p-type ZnO thin film and the correlative several important breakthroughs in ZnO homo-junction devices based on succeeding on fabrication of p-type ZnO film. Although the achievement obtained as summarized, there is also a long way from the real application of ZnO-based optoelectronic device. We here also discuss the problem and relevant possible solution for the fabrication of p-type ZnO film and its optoelectronic application. And forecast the preparation trends of p-type ZnO thin film.     

Analysis of single junction a-Si:H solar cells grown on different TCO’s

In consequence of previous investigation of individual transparent conductive oxide (TCO) and absorber layers a study was carried out on hydrogenated amorphous silicon (a-Si:H) solar cells with diluted intrinsic a-Si:H absorber layers deposited on glass substrates covered with different TCO films. The TCO film forms the front contact of the super-strata solar cell and has to exhibit good electrical (high conductivity) and optical (high transmittance) properties. In this paper we focused our attention on the influence of using different TCO’s as a front contact in solar cells with structure as follows: Corning glass substrate/TCO (800, 950 nm)/p-type μc-Si:H (∼5 nm)/p-type a-Si:H (10 nm)/a-SiC:H buffer layer (∼5 nm)/intrinsic a-Si:H absorber layer with dilution R = [H₂]/[SiH₄] = 20 (300 nm)/n-type a-Si:H layer (20 nm)/Ag + Al back contact (100 + 200 nm). Diode sputtered ZnO:Ga, textured and non-textured ZnO:Al [3] and commercially fabricated ASAHI (SnO₂:F) U-type TCO’s have been used. The morphology and structure of ZnO films were altered by reactive ion etching (RIE) and post-deposition annealing.It can be concluded that the single junction a-Si:H solar cells with ZnO:Al films achieved comparable parameters as those prepared with commercially fabricated ASAHI U-type TCO’s.     

Liquid phase epitaxial growth of pure and doped GaSb layers: morphological evolution and native defects

Undoped and Te-doped gallium antimonide (GaSb) layers have been grown on GaSb bulk substrates by the liquid phase epitaxial technique from Ga-rich and Sb-rich melts. The nucleation morphology of the grown layers has been studied as a function of growth temperature and substrate orientation. MOS structures have been fabricated on the epilayers to evaluate the native defect content in the grown layers from theC-V characteristics. Layers grown from antimony rich melts always exhibitp-type conductivity. In contrast, a type conversion fromp- ton- was observed in layers grown from gallium rich melts below 400 C. The electron mobility of undopedn-type layers grown from Ga-rich melts and tellurium doped layers grown from Sb- and Ga-rich solutions has been evaluated. Paper presented at the poster session of MRSI AGM VI. Kharagpur. 1995