Dielectric function model for p-type semiconductor inter-valence band transitions

2011 ◽  
Vol 109 (10) ◽  
pp. 103528 ◽  
Author(s):  
Yan-Feng Lao ◽  
A. G. Unil Perera
Keyword(s):  
Valence Band ◽  
Dielectric Function ◽  
Function Model ◽  
Type Semiconductor ◽  
P Type

Synthesis, crystal structure and thermoelectric properties of a new metal telluride Ba3Ag3InTe6

2017 ◽  
Vol 4 (9) ◽  
pp. 1458-1464 ◽  
Author(s):  
M.-Y. Lee ◽  
D. I. Bilc ◽  
E. Symeou ◽  
Y.-C. Lin ◽  
I.-C. Liang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Transport Properties ◽  
Valence Band ◽  
Thermoelectric Properties ◽  
Type Semiconductor ◽  
P Type

A new p-type semiconductor Ba3Ag3InTe6 with transport properties dominated by the layer [Ag3Te4]5− distributed in the valence band.

scholarly journals A Metastable p-Type Semiconductor as a Defect-Tolerant Photoelectrode

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6830
Author(s):  
Zahirul Sohag ◽  
Shaun O’Donnell ◽  
Lindsay Fuoco ◽  
Paul A. Maggard
Keyword(s):  
Valence Band ◽  
Crystalline Structure ◽  
Surface Oxidation ◽  
Defect Tolerance ◽  
Defect States ◽  
Powder Density ◽  
Type Semiconductor ◽  
Recombination Centers ◽  
Gap States ◽  
P Type

A p-type Cu3Ta7O19 semiconductor was synthesized using a CuCl flux-based approach and investigated for its crystalline structure and photoelectrochemical properties. The semiconductor was found to be metastable, i.e., thermodynamically unstable, and to slowly oxidize at its surfaces upon heating in air, yielding CuO as nano-sized islands. However, the bulk crystalline structure was maintained, with up to 50% Cu(I)-vacancies and a concomitant oxidation of the Cu(I) to Cu(II) cations within the structure. Thermogravimetric and magnetic susceptibility measurements showed the formation of increasing amounts of Cu(II) cations, according to the following reaction: Cu3Ta7O19 + x/2 O2 → Cu(3−x)Ta7O19 + x CuO (surface) (x = 0 to ~0.8). With minor amounts of surface oxidation, the cathodic photocurrents of the polycrystalline films increase significantly, from <0.1 mA cm−2 up to >0.5 mA cm−2, under visible-light irradiation (pH = 6.3; irradiant powder density of ~500 mW cm−2) at an applied bias of −0.6 V vs. SCE. Electronic structure calculations revealed that its defect tolerance arises from the antibonding nature of its valence band edge, with the formation of defect states in resonance with the valence band, rather than as mid-gap states that function as recombination centers. Thus, the metastable Cu(I)-containing semiconductor was demonstrated to possess a high defect tolerance, which facilitates its high cathodic photocurrents.

scholarly journals STUDY OF THERMOMETRIC MATERIAL Er1-xScxNiSb. II. EXPERIMENTAL RESULTS

2021 ◽  
Vol 82 (3) ◽  
pp. 5-11
Author(s):  
Volodymyr Krayovskyy ◽  
◽  
Volodymyr Pashkevych ◽  
Andriy Horpenuk ◽  
Volodymyr Romaka ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Fermi Level ◽  
Valence Band ◽  
Structural Defects ◽  
Type Semiconductor ◽  
Thermopower Coefficient ◽  
Temperature Activation ◽  
P Type ◽  
Thermometric Material

The results of a comprehensive study of the crystal and electronic structures, kinetic and energetic performances of the semiconductor thermometric material Er1-xScxNiSb, (x=0–0.1) are presented. Microprobe analysis of the concentration of atoms on the surface of Er1-xScxNiSb samples established their correspondence to the initial compositions of the charge, and the diffractograms of the samples are indexed in the structural type of MgAgAs. Because the atomic radius Sc (rSc=0.164 nm) is smaller than that of Er (rEr=0.176 nm), it is logical to reduce the values of the unit cell's period a(x) Er1-xScxNiSb, which correlate with the results of mathematical modeling. The temperature dependences of the resistivity ln(ρ(1/T)) contain high- and low-temperature activation regions, which are specific for semiconductors and indicate the location of the Fermi level in the bandgap, and positive values of the thermopower coefficient a(x, T) specify its position – near the valence band . This result does not agree with the results of modeling the electronic structure for its ordered version. The presence of a low-temperature activation region on the ln(ρ(1/T)) p-ErNiSb dependence with an activation energy =0.4 meV indicates the compensation of the sample provided by acceptors and donors of unknown origin. A decrease in the values of the resistivity ρ(x, T) and the thermopower coefficient a(x, T) points to an increase in the concentration of holes in p-Er1- xScxNiSb in the area of concentrations x=0–0.03. This is possible in a p-type semiconductor only by increasing the concentration of the main current carriers, which are holes. The fact of increasing the concentration of acceptors in Er1-xScxNiSb at insignificant concentrations of impurity atoms is also indicated by the nature of the change in the values of the activation energy of holes from the Fermi level to the valence band . Consequently, if in p-ErNiSb the Fermi level was at a distance of 45.4 meV from the level of the valence band , then at the concentration Er1-xScxNiSb, x=0.01, the Fermi level shifted towards the valence band and was located at a distance of 13.6. Since the Fermi level reflects the ratio of ionized acceptors and donors in the semiconductor, its movement by x=0.01 to the valence band is possible either with an increase in the number of acceptors or a rapid decrease in the concentration of ionized donors. At even higher concentrations of Sc impurity in p-Er1-xScxNiSb, x≥0.03, low-temperature activation sites appear on the ln(ρ(1/T)) dependences, which is a sign of compensation and evidence of the simultaneous generation of acceptor and donor structural defects in the crystal nature. This is also indicated by the change in the position of the Fermi level in the bandgap of the semiconductor Er1-xScxNiSb, which is almost linearly removed from the level of the valence band : (x=0.05)=58.6 meV and (x=0.10)=88.1 meV. Such a movement of the Fermi level during doping of a p-type semiconductor is possible only if donors of unknown origin are generated. For a p-type semiconductor, this is possible only if the concentration of the main current carriers, which are free holes, is reduced, and donors are generated that compensate for the acceptor states. This conclusion is also confirmed by the behavior of the thermopower coefficient a(x, T) at concentrations x≥0.03. The results of structural, kinetic, and energy studies of the thermometric material Er1-xScxNiSb allow us to speak about a complex mechanism of simultaneous generation of structural defects of acceptor and donor nature. However, the obtained array of experimental information does not allow us to unambiguously prove the existence of a mechanism for generating donors and acceptors. The research article offers a solution to this problem. Having the experimental results of the drift rate of the Fermi level as the activation energy (x) from the Fermi level to the valence band by calculating the distribution of the density of electronic states (DOS) sought the degree of compensation, which sets the direction and velocity of the Fermi level as close as possible to the experimental results. DOS calculations are performed for all variants of the location of atoms in the nodes of the unit cell, and the degree of occupancy of all positions by their own and/or foreign atoms. It turned out that for ErNiSb the most acceptable option is one that assumes the presence of vacancies in positions 4a and 4c of the Er and Ni atoms, respectively. Moreover, the number of vacancies in the position Er (4a) is twice less than the number of vacancies in the position Ni (4c). This proportion is maintained for Er1-xScxNiSb. Vacancies in the positions of Er (4a) and Ni (4c) atoms Er1-xScxNiSb are structural defects of acceptor nature, which generate two acceptor zones and in the semiconductor. The introduction of impurity Sc atoms into the ErNiSb structure by substituting Er atoms in position 4a is also accompanied by the occupation of vacancies by Sc atoms and a reduction in their number. Occupying a vacancy, the Sc atom participates in the formation of the valence band and the conduction band of the semiconductor Er1-xScxNiSb, acting as a source of free electrons. We can also assume that the introduction of Sc atoms into the structure of the compound ErNiSb is accompanied by a process of ordering the structure of Er1-xScxNiSb and Ni atoms occupy vacancies in position 4c. This process also, however, 2 times slower, leads to a decrease in the concentration of structural defects of acceptor nature. In this case, Ni, giving valence electrons, now act as donors.

The optical bandgap and band-edge positions of semiconducting p-type CuYO2

1985 ◽  
Vol 63 (10) ◽  
pp. 1306-1308 ◽  
Author(s):  
F. A. Benko ◽  
F. P. Koffyberg
Keyword(s):  
Valence Band ◽  
Optical Transition ◽  
Optical Bandgap ◽  
Band Edge ◽  
Valence Band Edge ◽  
Vacuum Level ◽  
Type Semiconductor ◽  
P Type

CuYO2, doped with calcium, is a low-mobility p-type semiconductor. From photoelectrochemical measurements it is found that the valence band edge is 5.3 eV below the vacuum level, typical for oxides with a metal-3d valence band. The lowest bandgap is 1.20 eV and the transition is indirectly allowed. An optical transition at 3.60 eV indicates an oxygen-2p valence band at 7.7 eV below vacuum. The results are discussed with the help of a simplified band scheme.

Transparent P-type Conducting LaCuOS Layered Oxysulfide

2001 ◽  
Vol 666 ◽  
Author(s):  
Kazushige Ueda ◽  
Shin-ichiro Inoue ◽  
Sakyo Hirose ◽  
Hiroshi Kawazoe ◽  
Hideo Hosono
Keyword(s):  
Electrical Conductivity ◽  
Visible Region ◽  
Optoelectronic Devices ◽  
Promising Material ◽  
High Transparency ◽  
Conducting Oxides ◽  
Excitonic Absorption ◽  
Type Semiconductor ◽  
Optical Applications ◽  
P Type

ABSTRACTMaterials design for transparent p-type conducting oxides was extended to oxysulfide system. LaCuOS was selected as a candidate for a transparent p-type semiconductor. It was found that the electrical conductivity of LaCuOS was p-type and controllable from semiconducting to semi-metallic states by substituting Sr2+ for La3+. LaCuOS films showed high transparency in the visible region, and the bandgap estimated was approximately 3.1 eV. Moreover, it was revealed that LaCuOS showed sharp excitonic absorption and emission at the bandgap edge, which is advantageous for optical applications. A layered oxysulfide, LaCuOS, was proposed to be a promising material for optoelectronic devices.

The Study of p-n and Schottky Junction for Magnetodiode

2011 ◽  
Vol 378-379 ◽  
pp. 663-667 ◽  
Author(s):  
Toempong Phetchakul ◽  
Wittaya Luanatikomkul ◽  
Chana Leepattarapongpan ◽  
E. Chaowicharat ◽  
Putapon Pengpad ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electrical Properties ◽  
Simulation Model ◽  
Hall Effect ◽  
Schottky Junction ◽  
Field Sensitivity ◽  
Field Response ◽  
Type Semiconductor ◽  
Simulation Results ◽  
P Type

This paper presents the simulation model of Dual Magnetodiode and Dual Schottky Magnetodiode using Sentaurus TCAD to simulate the virtual structure of magneto device and apply Hall Effect to measure magnetic field response of the device. Firstly, we use the program to simulate the magnetodiode with p-type semiconductor and aluminum anode and measure electrical properties and magnetic field sensitivity. Simulation results show that sensitivity of Dual Schottky magnetodiode is higher than that of Dual magnetodiode.

Study on Phases and Thermoelectric Properties of Bulk Fe4Sb12 and Fe3CoSb12 Prepared by Milling and Sintering

2011 ◽  
Vol 121-126 ◽  
pp. 1526-1529
Author(s):  
Ke Gao Liu ◽  
Jing Li
Keyword(s):  
Thermoelectric Properties ◽  
Impurity Phase ◽  
Semiconductor Materials ◽  
Thermal Constant ◽  
X Ray Diffraction ◽  
X Ray ◽  
Seebeck Coefficients ◽  
Maximum Value ◽  
Type Semiconductor ◽  
P Type

Bulk Fe4Sb12 and Fe3CoSb12 were prepared by sintering at 600 °C. The phases of samples were analyzed by X-ray diffraction and their thermoelectric properties were tested by electric constant instrument and laser thermal constant instrument. Experimental results show that, the major phases of bulk samples are skutterudite with impurity phase FeSb2. The electric resistivities of the samples increase with temperature rising at 100~500 °C. The bulk samples are P-type semiconductor materials. The Seebeck coefficients of the bulk Fe4Sb12 are higher than those of bulk Fe3CoSb12 samples at 100~200 °C but lower at 300~500 °C. The power factor of the bulk Fe4Sb12 samples decreases with temperature rising while that of bulk Fe3CoSb12 samples increases with temperature rising at 100~500 °C. The thermal conductivities of the bulk Fe4Sb12 samples are relatively higher than those of and Fe3CoSb12, which maximum value is up to 0.0974 Wm-1K-1. The ZT value of bulk Fe3CoSb12 increases with temperature rising at 100~500 °C, the maximum value is up to 0.031.The ZT values of the bulk Fe4Sb12 samples are higher than those of bulk Fe3CoSb12 at 100~300 °C while lower at 400~500 °C.

First-Principles Study on the Conductive Properties of P-Doped ZnO

2009 ◽  
Vol 79-82 ◽  
pp. 1253-1256 ◽  
Author(s):  
Li Guan ◽  
Qiang Li ◽  
Xu Li ◽  
Jian Xin Guo ◽  
Bo Geng ◽  
...  
Keyword(s):  
Fermi Level ◽  
Valence Band ◽  
Density Functional ◽  
Lattice Structure ◽  
Mulliken Charge ◽  
Total Density ◽  
Type Conductivity ◽  
Doped Zno ◽  
P Type ◽  
Conductive Properties

In the present paper, the lattice structure, band structure and density of state of pure and P-doped ZnO are calculated by first-principle method based on density functional theory. By analyzing the Mulliken charge overlap population and bond length, it is found that the bond of P-Zn is longer and stronger than O-Zn bond for PO-ZnO. But for PZn-ZnO, the O-P bond becomes shorter and more powerful than O-Zn bond. Also, weak O-O bonds are formed in this case. Our results show that the final total energy of PO-ZnO is lower than PZn-ZnO. The lattice structure of PO-ZnO is more stability than PZn-ZnO. For PO-ZnO, The Fermi level moves into the valence band, which expresses that the holes appear on the top of valence band and thus the PO-ZnO exhibits p-type conductivity. For PZn-ZnO, the Fermi level moves up to the conductor band and the total density of states shifts to the lower energy region, thus PZn-ZnO shows the n-type conductivity.

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