We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

Over the past three decades a new spectroscopic technique with unique possibilities has emerged. Based on coherent and time-resolved detection of the electric field of ultrashort radiation bursts in the far-infrared, this technique has become known as terahertz time-domain spectroscopy (THz-TDS). In this review article the authors describe the technique in its various implementations for static and time-resolved spectroscopy, and illustrate the performance of the technique with recent examples from solid-state physics and physical chemistry as well as aqueous chemistry. Examples from other fields of research, where THz spectroscopic techniques have proven to be useful research tools, and the potential for industrial applications of THz spectroscopic and imaging techniques are discussed.

Terahertz spectroscopy and imaging – Modern techniques and applications

The scaling of complementary metal oxide semiconductor transistors has led to the silicon dioxide layer, used as a gate dielectric, being so thin (14?nm) that its leakage current is too large It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (?) or 'high K' gate oxides such as hafnium oxide and hafnium silicate These oxides had not been extensively studied like SiO2, and they were found to have inferior properties compared with SiO2, such as a tendency to crystallize and a high density of electronic defects Intensive research was needed to develop these oxides as high quality electronic materials This review covers both scientific and technological issues?the choice of oxides, their deposition, their structural and metallurgical behaviour, atomic diffusion, interface structure and reactions, their electronic structure, bonding, band offsets, electronic defects, charge trapping and conduction mechanisms, mobility degradation and flat band voltage shifts The oxygen vacancy is the dominant electron trap It is turning out that the oxides must be implemented in conjunction with metal gate electrodes, the development of which is further behind Issues about work function control in metal gate electrodes are discussed

https://iopscience.iop.org/article/10.1088/0034-4885/69/2/R02/pdf

High dielectric constant gate oxides for metal oxide Si transistors

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

The scaling of complementary metal oxide semiconductor (CMOS) transistors has led to the silicon dioxide layer used as a gate dielectric becoming so thin (1.4 nm) that its leakage current is too large. It is necessary to replace the SiO2 with a physically thicker layer of oxides of higher dielectric constant (κ) or 'high K' gate oxides such as hafnium oxide and hafnium silicate. Little was known about such oxides, and it was soon found that in many respects they have inferior electronic properties to SiO2 ,s uch as a tendency to crystallise and a high concentration of electronic defects. Intensive research is underway to develop these oxides into new high quality electronic materials. This review covers the choice of oxides, their structural and metallurgical behaviour, atomic diffusion, their deposition, interface structure and reactions, their electronic structure, bonding, band offsets, mobility degradation, flat band voltage shifts and electronic defects. The use of high K oxides in capacitors of dynamic random access memories is also covered.

/pdf/high-dielectric-constant-oxides-cotu2e70vd.pdf

High dielectric constant oxides

The oval defect has been an ubiquitous problem in GaAs epitaxial layers grown by MBE. Their reported density varies from about 100 cm 2 (best case) to about 10 000 cm 2. A recent report by Calawa, et al., I shows that oval defect formation is associated with Ga droplets which appear on the epilayer surface during growth. In this paper we report for the first time the deposition of epitaxial layers of GaAs by MBE which are entirely free of oval defects. The oval-defect-free layers were grown on a 1.6 cm2 (100) semi-insulating GaAs substrate at 550 ·C, at growth rates of 0.4-1.0 Jllh. The critical factor in obtaining oval-defect-free layers was the presence of a Mg flux corresponding to a magnesium content of about 10 cm -3. A careful metallurgical inspection of these layers using Nomarski phase constrast microscopy at magnifications up to 1600X revealed no oval defects. The hole concentrations ofthese layers were approximately 10 cm-3. Layers grown without high-level Mg doping under otherwise identical conditions had oval defect densities in the 300 cm 2 range. Gallium spitting from the gallium effusion cell has long been suspected as the primary means of droplet generation. Magnesium doping should not eliminate this source, therefore we conclude that gallium spitting is not the source of gallium droplets on the substrate surface. The remaining plausible mechanism for the formation of gallium droplets on the substrate surface is the nucleation of droplets from adsorbed gallium. When the growth surface is allowed to accumulate large quantities of gallium, many droplets form and huge oval defect concentrations result. A GaAs layer grown fo]]owing exposure to about 100 monolayers of gallium had an oval defect concentration of about 10 cm -2. The growth of oval-defect-free layers indicates that this nucleation is not spontaneous under arsenic-stable conditions. Rather, sites of surface imperfections or contamination must act as nucleating centers for gallium. However, some growth irregularities indicative of surface contamination are commonly observed and are not oval defects. Thus, only certain defects or contaminants cause the oval defect. Gallium commonly requires its oxide species to wet otherwise inert surfaces, and will not wet in vacuum certain surfaces it readily wets in the presence of atmospheric oxygen and water vapor. One might expect that a precipitate at least partly composed of gallium oxides would serve as an ideal site to nucleate a gallium droplet. Mg is ap-type dopant in MBE GaAs that is known to have a lower electrical activity than is expected from the incident flux. 1Jte model most consistent with available data indicates that the reduced activity is due to the incorporation of an electrically inactive species ofMg: that species is believed to be MgO. This indicates the existence of oxygen-containing species that readily form MgO in the presence of Mg. Ga20 (gallium suboxide) is an oxide species observable in the gallium cell's effusate.2 Intentionally increasing the Ga20 flux from the Ga effusion cell has been shown 3 to markedly increase oval defect densities. Ga20 3 is formed by the disproportionation of the suboxide. It is believed that this forms oxide precipitates that nucleate gallium droplet formation, thus forming the precursor of the oval defect. Moreover, the disproportionation reaction yields unbonded Ga atoms that may trigger the Ga droplet nucleation. In the presence of large fluxes of magnesium, the gallium oxides are reduced on the sample surface, forming MgO. MgO is not wet by Ga in vacuum, thus it is unlikely that macroscopic gallium droplets will be nucleated by MgO. We performed experiments to enhance the formation of Ga20 3 precipitates in an attempt to induce Ga droplet formation and thereby increase the oval defect density. We used an independent source ofG~O, consisting of an effusion cell charged with both Ga and Ga20 3. This allowed stable control of the Ga20 flux independent of the gallium source used for growth. A Ga20 pressure of about 5 X 109 Torr at the substrate resulted in an oval defect density of lOS _106 cm 2. Optical properties were affected as well. The near-band-edge photoluminescence intensity at 2 K was reduced approximately tenfold compared to control specimens grown with the Ga20 source shuttered. These control layers exhibited oval defect densities of 200-500 cm-2. In conclusion, the role of gallium droplets in the formation of oval defects is supported. The elimination of oval defects through the use of magnesium doping indicates that these Ga droplets do not originate externally to the surface, i.e., at the gallium effusion cell. Rather, it is believed that nucleating centers on the sample surface support Ga droplet formation. It is found that a sufficient quantity of magnesium disrupts this mechanism. The reactivity of magnesium and its observed doping behavior indicates that at least some magnesium is incorporated as MgO (at the 10 cm-3 level, about 9O%!). This, in tum, suggests that in the absence of sufficient quantities of Mg, G~03 is incorporated as precipitates. Ga203 precipitates can nucleate Ga droplet formation: Enhancing oxide incorporation with an additional Ga20 source drastically increases the oval defect concentration. Gallium oxide species are eliminated via reactions with Mg fluxes. For properly prepared surfaces free from other nucleating centers, this results in oval-defect-free epilayers. Our results and interpretation are consistent with the accepted origins of the oval defect I and the observed doping

Summary Abstract: The MBE growth of GaAs free of oval defects

A model is presented which relates the observed effects of substrate temperature and growth flux magnitudes upon layer quality to the presence of volatile oxides and the thermodynamics of the formation of nonvolatile oxides on the growth surface. A means for reducing oxide contamination is presented and the consequent benefits explored.

Volatile metal‐oxide incorporation in layers of GaAs, Ga1−xAlxAs and related compounds grown by molecular beam epitaxy

We have characterized thin films of LaScO3 and LaAlO3 which were grown by molecular beam deposition on Si substrates. Samples of LaScO3 were also grown by pulsed laser deposition on MgO substrates. Using transmission studies between 1.5 and 6eV, we have established that low temperature deposition leads to a reduced band gap with respect to the bulk crystal. Furthermore, using spectroscopic ellipsometry from 5to9eV we observe substantial differences in near-band gap absorption between thin and thicker films for both materials. We obtain a band gap of 5.84eV for the thinner film of LaAlO3, whereas we find a band gap of 6.33eV for the thicker film of LaAlO3. Similarly we find band gaps of 5.5 and 5.96eV, respectively, for thin and thick films of LaScO3.

Optical properties of La-based high-K dielectric films

We have studied the formation and properties of ≊15 nm films of Pd on GaAs(100) and (110) substrates as a function of annealing temperature. Ultraviolet and x–ray photoelectron spectra (UPS and XPS) have established several distinctive phases; coupled with scanning electron microscopy studies, agglomeration has been observed at elevated temperatures. Transmission electron diffraction studies permit more detailed phase identification at specific temperatures. Electrical studies permit characterization of both interface properties and bulk transport properties of the reacted layer. In contrast to previous work, we find no Pd–As binary phases. After high temperature anneals (Ta >350 °C), only PdGa is observed; these films are not continuous, but form [often epitaxial on (100) substrates—with (110)PdGa‖‖ (100)GaAs and [111]‖‖[011]GaAs] islands. After low temperature (≊250 °C) anneals of Pd films on (110) substrates, small crystallites of PdGa are imbedded in the dominant matrix of a ternary single crystal ph...

Palladium on GaAs: A reactive interface

Epitaxial rare-earth scandate thin films of 100–1500 nm in thickness have been prepared by pulsed laser deposition on SrTiO3(100) and MgO(100) substrates. Stoichiometry and crystallinity were investigated by Rutherford backscattering spectrometry/channelling (RBS/C), transmission electron microscopy, and X-ray diffraction. Electrical measurements on microstructured capacitors with a SrRuO3 bottom electrode and Au top contacts reveal dielectric constants of 20 to 27, leakage currents of 0.85 to 6 μA/cm2 at 250 kV/cm, and breakdown fields of 0.6 to 1.2 MV/cm. The optical bandgaps of the films range from 5.5 to 6 eV. The results substantiate the high potential of rare-earth scandates as alternative gate oxides.

John L. Freeouf

Papers

Summary Abstract: The MBE growth of GaAs free of oval defects

Volatile metal‐oxide incorporation in layers of GaAs, Ga1−xAlxAs and related compounds grown by molecular beam epitaxy

Optical properties of La-based high-K dielectric films

Palladium on GaAs: A reactive interface

Growth and properties of epitaxial rare-earth scandate thin films