G. Lamedica

Properties of ZrO2 thin films prepared by laser ablation

Abstract ZrO2 thin films have been prepared by laser ablation of Zr or ZrO2 targets in oxygen reactive atmosphere. The influence of the deposition parameters as oxygen pressure and target composition on the structure and morphology of the deposited layers has been studied. Scanning electron microscopy, secondary ion mass spectroscopy and dielectric constant measurements have been performed to characterize the deposited layers. Dielectric constant values in the range 15–20 and low losses were evidenced for samples prepared in a narrow range of experimental conditions.

Porous Silicon: A Buffer Layer for PbS Heteroepitaxy

In the present work, we report on the heteroepitaxial growth of PbS on porous silicon (PS). Epitaxial PbS films were grown by MBE on the surface of PS formed on the n+-type silicon (111) substrate. The films were comparable with films grown on BaF2 substrates. Beneficial influence of a PS buffer layer on the structure and properties of PbS epitaxial films was supported by implementation of sensitive Schottky-barrier photodiodes fabricated in these films.

Oxidized Porous Silicon: From Dielectric Isolation to Integrated Optical Waveguides

A brief review of 20-years research of formation, processing and utilizing of oxidized porous silicon (OPS) is presented. Electrolytes to form porous silicon (PS) layers, special features of PS chemical cleaning and thermal oxidation are discussed. OPS application for dielectric isolation of components of bipolar ICs and for the formation of silicon-on-insulator structures has been demonstrated. Although these OPS-based techniques have found limited current commercial use, experience gained is applicable to the fabrication of optoelectronic devices. Specifically, integrated optical waveguides based on OPS have been developed.

Er-doped oxidised porous silicon waveguides

Abstract The present work reports Er-doped channel oxidized porous silicon waveguides (OPSWG) formed from n + -type Si by the two-step anodisation process. Er has been introduced into porous silicon before oxidation by a cathodic treatment in 0.1 M Er (NO 3 ) 3 aqueous solution. A correlation between Er concentration and refractive index profiles has shown dominant core doping with Er relative to cladding regions. Reported Er concentration of 0.8 at.% in the OPSWG is large enough to attain the amplification effect.

A MODEL OF RADIATIVE RECOMBINATION IN N-TYPE POROUS SILICON-ALUMINUM SCHOTTKY JUNCTION

It is common knowledge that silicon emits visible light in its breakdown condition, but it is also known to have low efficiency. In this letter, we report an in-depth analysis of data for light emitting devices based on porous silicon. A theoretical model of luminescence from reverse biased p-n junction has been developed for this n-type porous silicon–aluminium Schottky junction to explain the higher efficiency of these electroluminescence devices in comparison with that from a reverse biased p-n junction structure. Through this model, it is possible to understand the steps that are necessary to improve the efficiency of porous-aluminum Schottky junction.

X-ray diffractometry of Si epilayers grown on porous silicon

Abstract X-ray double-crystal diffractometry was used to measure lattice deformation of porous silicon (PS) and Si epitaxial layers grown on PS. PS layers 1–10 μm in thickness and 15-65% in porosity were formed by anodization of n + -type Sb doped Si wafers in a 12% HF aqueous solution. Lattice deformations of both PS and epitaxial layers are shown to strongly depend on PS porosity. Grown on uniform PS 40–60% in porosity, the epilayers, single-crystal as they are, display high lattice deformation and defect density. Epilayers grown on two-layer PS are comparable with the films grown on the n + -type single-crystal Si substrate.

High-amplitude high-frequency oscillations of temperature, electron–hole pair concentration, and current in silicon-on-insulator structures

Interacting oscillations of the current, lattice temperature, and concentration of thermally generated electron–hole pairs were discovered in silicon films of silicon-on-insulator structures upon their heating with extremely high current. The nature of the oscillations discovered is fundamentally different from what has yet been known. They occur owing to two competing processes: the thermal generation of electron–hole pairs, and the pair concentration reduction caused by the current flowing through the silicon film with nonuniform temperature field. In our experiments the current density reached 1.5×105 A/cm2 and the specific power dissipated in the silicon film exceeded 3.6 GW/cm3. We observed the oscillation frequencies up to 3 MHz and variations of the current and pair concentration were more than tenfold, while the temperature varied from 700–740 to 950–1300 K.

Optoelectronics silicon on insulator integrated circuits by porous silicon technology

This work reports on the CMOS-SOI devices based on porous silicon technology (PST) opening the possibility of wafer scale integration realizing on-chip optoelectronic integrated circuits by the PST. Silicon on insulator (SOI) structure based on the preferential anodization of n+ layer within n-/n+/n- were realized. Standard n-type Si (100) have been used as initial substrates. N+ layer have been formed by Sb ion implantation into the front and backside of the substrates followed by annealing. Then an epitaxial layer has been grown on the front of the wafers and projection photolithography using reactive ion etching of both the mask and the epitaxial layer has been used to define three dimensional pattern of islands wherein device components are formed. Characteristics and device layout are presented for partially depleted devices used to build ring oscillator showing that a 1.2 micron resolution in SOI porous silicon technology is comparable with a 0.5 micron CMOS technology.

Investigation of Morphology of Porous Silicon Formed on N+ Type Silicon

The properties of porous silicon (PS) are closely connected to its morphology, much investigation has been done in order to correlate the morphological characteristics of PS with the anodisation parameters. In this paper the results of morphological analysis of PS formed on N+type substrates of 〈1 0 0〉 and 〈1 1 1〉 orientation are presented. The dependences of the porosity, thickness of PS, density of pores and of the effective surface on the current density are obtained. Interpretation of these results in terms of diffusion layer and energy levels is given, with special attention given to the low current density case.

Oxidized Porous Silicon Based SOI: Untapped Resources

This paper discusses new potentialities of oxidized porous silicon (PS) based SOI structures that have hitherto escaped attention of the researchers. Oxidized PS (OPS) has the property of controlling its characteristics depending on regimes of formation of PS layer and its further oxidation. The manner by which electrical and optical properties of the OPS layer may be varied with oxidation regimes of PS layers with various porosities is presented. It is of great importance that oxidized PS regions of different characteristics (porosity, thickness etc.) may be formed simultaneously within the same wafer.