Oxide-semiconductor interface quality of high-pressure reactive sputtered (HPRS) TiO 2 films annealed in O 2 at temperatures ranging from 600 to 900 • C, and atomic layer deposited (ALD) TiO 2 films grown at 225 or 275 • C from TiCl 4 or Ti(OC 2 H 5 ) 4 , and annealed at 750 • C in O 2 , has been studied on silicon substrates. Our attention has been focused on the interfacial state and disordered-induced gap state densities. From our results, HPRS films annealed at 900 • C in oxygen atmosphere exhibit the best characteristics, with D it density being the lowest value measured in this work (5-6 × 10 11 cm −2 eV −1 ), and undetectable conductance transients within our experimental limits. This result can be due to two contributions: the increase of the SiO 2 film thickness and the crystallinity, since in the films annealed at 900 • C rutile is the dominant crystalline phase, as revealed by transmission electron microscopy and infrared spectroscopy. In the case of annealing in the range of 600-800 • C, anatase and rutile phases coexist. Disorder-induced gap state (DIGS) density is greater for 700 • C annealed HPRS films than for 750 • C annealed ALD TiO 2 films, whereas 800 • C annealing offers DIGS density values similar to ALD cases. For ALD films, the studies clearly reveal the dependence of trap densities on the chemical route used.

We present the epitaxial growth of Ge and Ge 0.94 Sn 0.06 layers with 1.4% and 0.4% tensile strain, respectively, by reduced pressure chemical vapor deposition on relaxed GeSn buffers and the formation of high-k/metal gate stacks thereon. Annealing experiments reveal that process temperatures are limited to 350 °C to avoid Sn diffusion. Particular emphasis is placed on the electrical characterization of various high-k dielectrics, as 5 nm Al 2 O 3 , 5 nm HfO 2 , or 1 nmAl 2 O 3 /4 nm HfO 2 , on strained Ge and strained Ge 0.94 Sn 0.06 . Experimental capacitance− voltage characteristics are presented and the effect of the small bandgap, like strong response of minority carriers at applied field, are discussed via simulations.

In this paper, we present a detailed characterization of high quality layers of Si implanted with Ti at high doses. These layers are intended to the formation of an intermediate band ͑IB͒ solar cell. The main requirement to obtain an IB material is to reach an impurity concentration beyond the Mott limit, which is, in this case, much higher than the solid solubility limit. To overcome this limit we used the combination of ion implantation and pulsed-laser melting as nonequilibrium techniques. Time-of-flight secondary ion mass spectrometry measurements confirm that Ti concentration exceeds the theoretical Mott limit in the implanted layer, and glancing incidence x-ray diffraction and transmission electron microscopy measurements prove that good crystallinity can be achieved. Sheet resistance and Hall effect mobility show uncommon characteristics that can only been explained assuming the IB existence.

The effect of rapid thermal annealing processes on the properties of SiO 2.0 and SiN 1.55 films was studied. The films were deposited at room temperature from N 2 and SiH 4 gas mixtures, and N 2 , O 2 , and SiH 4 gas mixtures, respectively, using the electron cyclotron resonance technique. The films were characterized by Fourier transform infrared spectroscopy ͑FTIR͒ and electron paramagnetic resonance spectroscopy. According to the FTIR characterization, the SiO 2.0 films show continuous stress relaxation for annealing temperatures between 600 and 1000°C. The properties of the films annealed at 900-1000°C are comparable to those of thermally grown ones. The density of defects shows a minimum value for annealing temperatures around 300-400°C, which is tentatively attributed to the passivation of the well-known EЈ center Si dangling bonds due to the formation of Si-H bonds. A very low density of defects (5ϫ10 16 cm Ϫ3 ) is observed over the whole annealing temperature range. For the SiN 1.55 films, the highest structural order is achieved for annealing temperatures of 900°C. For higher temperatures, there is a significant release of H from N-H bonds without any subsequent Si-N bond healing, which results in degradation of the structural properties of the film. A minimum in the density of defects is observed for annealing temperatures of 600°C. The behavior of the density of defects is governed by the presence of non-bonded H and Si-H bonds below the IR detection limit.

room temperature to the short-wavelength infrared (SWIR) range (1.4-3 µm, i.e., 0.89-0.41 eV) has the potential to revolutionize silicon-based optoelectronic devices. The introduction of a complementary metaloxide semiconductor (CMOS) compatible process would enable the integration of optical and electronic functionality on a single chip. [1] Nowadays, several approaches are under intensive research to enhance Si SWIR photoresponse, such as the integration of III-V compound semiconductors with silicon, [2,3] photodetectors based on SiGe alloys [4,5] or HgCdTe/Si heterostructures. [6] Despite their high performances, these devices suffer from several drawbacks: they are based on nonabundant or contaminant materials, they usually require cryogenic temperatures to operate, and they are hardly integrated into the very mature Si-CMOS fabrication routes, adding considerable cost and complexity to photonic circuit manufacturing.An alternative path to increase the Si SWIR photoresponse that would avoid the hybrid integration of Si technology with unconventional materials is the direct modification of its electronic band structure. From this perspective it is possible to find interesting approaches. One is the use of a laser-crystallization process to induce an anisotropic tensile stress in silicon optical fibers. This way the bandgap can be reduced from 1.11 to 0.59 eV. [7] Unfortunately, the fiber structure hinders its incorporation into planar imaging arrays. A different method, that has attracted recently great attention, [8] is the extrinsic sub-bandgap photoresponse obtained from the incorporation of deep-level impurities at concentrations far above their equilibrium values. Single-crystalline silicon layers with transition metals (Ti, V, Au, and Ag) or chalcogens (S, Se, and Te) at concentrations above 10 19 cm -3 have been obtained by means of ion implantation and subsecond annealing techniques (in a process denominated as supersaturation or hyperdoping). We have shown that silicon hyperdoped with Ti [9,10] or V [11] presents outstanding properties such as a sub-bandgap optical absorption coefficient in the 10 4 cm -1 range [12] or a photoconductive response extended down to 0.2 eV (6.2 µm) at cryogenic temperatures. [13] Gold hyperdoped [14,15] or silver hyperdoped [16] This work deepens the understanding of the optoelectronic mechanisms ruling hyperdoped-based photodevices and shows the potential of Ti hyperdoped-Si as a fully complementary metal-oxide semiconductor compatible material for room-temperature infrared photodetection technologies. By the combination of ion implantation and laser-based methods, ≈20 nm thin hyperdoped single-crystal Si layers with a Ti concentration as high as 10 20 cm −3 are obtained. The Ti hyperdoped Si/p-Si photodiode shows a room temperature rectification factor at ±1 V of 509. Analysis of the temperature-dependent current-voltage characteristics shows that the transport is dominated by two mechanisms: a tunnel mechanism at low bias and a recombination process in the space charge...