Author: OLEKSANDR MALIK

Device application of non-equilibrium MOS capacitors fabricated on high resistivity silicon

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE (2011)

This work shows that the direct pulse-wide-modulated (PWM) output electric signal, with a duty cycle controlled by light intensity, can be obtained using a circuit that contains a saw-tooth voltage generator connected in series with a dc voltage source and a metal (semitransparent gate) oxide semiconductor capacitor (MOS-C) operating in non-equilibrium mode. Amplified output signal presents positive and negative PWM waveforms that can be easily separated using diodes. The duty of the positive part is proportional to the light intensity, whereas for the negative part is inversely proportional to the intensity. The frequency operating range of this proposed instrument varies from 1 Hz to a few kilohertz. The duty cycle of the PWM output signal varies from 2 to 98 % when the incident light intensity is varying in the microwatts range. This new transducer could be useful for automatic control, robotic applications, dimmer systems feedback electronic systems, and non-contact optical position sensing for nulling and centering measurements. The detailed description of the physical and operating principles of this invented transducer are presented.

Article

MOS-capacitor Silicon Pulse-width modulation Nulling and centering measurements CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA ELECTRÓNICA

Digital output silicon optical sensors

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE CARLOS ZUÑIGA ISLAS (2008)

For the first time, a detailed description of lowcost newintelligent (or smart) two-terminal optoelectronic devices without any on-chip circuitry for signal processing is presented. The design of the devices is based on the intelligent integration of micro-sized diodes and metal-oxide-semiconductor (MOS) capacitors. By combining physical processes and a functional voltage bias, such optical sensors transform the received analog input nonmodulated optical signal directly into a pulse-width modulated electrical signal; the duty of the signal depends on the irradiation level, and the whole process is conducted without any integrated or external analog-to-digital converter. When the optical sensors operate under a pulsed irradiation synchronized with the functional voltage bias, unconventional logic properties are obtained that can be used to identify the emission from two equal LEDs.

Article

Silicon Optical sensor Intelligent sensor Digital output CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

Pulse characteristics of silicon double barrier optical sensors with signal amplification

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE CARLOS ZUÑIGA ISLAS (2008)

The pulse characteristics of optical sensors with double potential barriers formed on the opposite sides of a high-resistivity (v) silicon substrate have been studied. The first barrier is formed by multiple micro-sized Ti–vSi contact barriers surrounded by Ti–SiO2–vSi MOS structures. The second one is the v–n+ potential barrier formed at the bottom of the wafer. The structure presents signal amplification for both polarities of the applied voltage. Under negative bias applied to the semi-transparent Ti-electrode, the reason of the current gain is the change in the transport mechanism of carriers through the potential barrier of the Schottky barrier along its perimeter, which is due to the strong electric field originated by the photogenerated minority carriers forming an inversion layer at the silicon-oxide interface. Under positive bias, the current gain is due to the operation of the v–n+ potential barrier, which was studied earlier, and in this work it is used for comparison purposes.

Article

Optical sensors Silicon Signal amplification Double barrier structures CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

The physical reason of intense electroluminescence in ITO–Si heterostructures

OLEKSANDR MALIK Arturo I. Martinez FRANCISCO JAVIER DE LA HIDALGA WADE (2007)

Intense electroluminescence from a spray deposited heavily tin-doped indium oxide (ITO)–n type silicon (Si) heterojunctions, presenting the properties of an induced p–n junction, has been observed. The role of the degenerated n-type ITO film as a good supplier of holes to maintain an inversion layer formed at the silicon interface is discussed. However, the physical mechanism responsible for a significantly higher quantum efficiency of the radiation emission from such structures is not clear. The explanation of this phenomenon, based on the confinement of carriers at the interface due to multi-point contacts between the ITO film and the silicon, is discussed.

Article

Indium oxide Thin film Silicon Heterojunction Electroluminescence CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA ELECTRÓNICA

Very shallow boron junctions in Si by implantation and SOD diffusion obtained by RTP

Jairo Plaza Castillo ALFONSO TORRES JACOME OLEKSANDR MALIK (2008)

Because of their very large integration capabilities and continuous scaling, the CMOS devices are the basic element in the currentintegrated circuits. Their scaling up to sub-micrometric scale presents advantages like diminution of power consumption, faster devices and a larger level of integration. But the physics limitations begin to be important at these dimensions, anomalous effects like hot electrons, leakage currents and punch through, among others, appear. These effects can be reduced if, at the source/drain region, shallow junctions are obtained with junction depth (xj) less than 200 nm. To achieve this goal, new junction fabrication methods, which include pre-amorphization [S.D. Kim, C.M. Park, J.C.S. Woo, Formation and control of box-shaped ultra-shallow junction using laser annealing and pre-amorphization implantation, Solid State Electron. 49 (2005) 131–135] are required. Other alternative techniques that do not require ion implantation [T. Uchino, P. Ashburn, Y. Kiyota, T. Shiba, A CMOS-compatible rapid vapor-phase doping process for CMOS scaling, IEEE Trans. Electron Devices 51(1) (2004) 14–19.], in order to prevent surface crystal damage and as a consequence the inhibition of boron interstitial clusters and {3 1 1} defects [R.T. Crosby, K.S. Jones, M.E. Law, L. Radic, Dislocation loops in silicon–germanium alloys: the source of interstitials, Appl. Phys. Lett. 87 (192111) (2005) 1–3.], which are the trigger of the ‘‘transient enhanced diffusion’’ (TED) process are used. In this essay, it is shown that rapid thermal process, allow the fabrication of very shallow junctions with a xj less than 300nm by using with high energies and high doses of boron/BF2 ions implantation. By this way the slow dissolution of the dislocation loops, present at the end of range (EOR) of the implanted boron, allow this process. These obtained junctions are compared with those prepared by using the spin on doping (SOD) technique. The diffusion profiles obtained by both processes and their electrical properties are measured and compared for their application as S–D regions in a current CMOS process.

Article

Shallow junctions Boron implants BF2 implants Boron SOD High boron concentration CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

Compositional and structural characterization of silicon nanoparticles embedded in silicon rich oxide

JOSE ALBERTO LUNA LOPEZ MARIANO ACEVES MIJARES OLEKSANDR MALIK JORGE EDUARDO RICKARDS CAMPBELL (2007)

Silicon Rich Oxide (SRO) is a dielectric material that contains Si nanoparticles, thus showing novel physical characteristics which permits

its use in optoelectronic devices. In this work, the composition and structure at the surface, volume and Si/SRO interface of the SRO films deposited on c-Si substrates were studied. Different techniques, such as Atomic Force Microscopy (AFM), High Resolution Transmission Electronic Microscopy (HRTEM), Rutherford Backscattering Spectrometry (RBS) and X-ray Photoelectron Spectroscopy (XPS) were used in the study. XPS and RBS reveal that the composition of the films varied with respect to the gas flow ratio. These results allow us to correlate the compositional and structural [as size of the grains (roughness), nc-Si size and different oxidation states of Si] changes of the surface, volume and interface from the SRO films with the flow ratio (Ro) used during the deposition process and with the high temperature annealing time.

Article

Silicon rich oxide AFM HRTEM Nanocrystals Surface roughness RBS XPS CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

UV-sensitive optical sensors based on ITO-gallium phosphide heterojunctions

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE CARLOS ZUÑIGA ISLAS JESUS HUMBERTO ABUNDIS PATIÑO (2010)

Design and characteristics of wide-band UV sensors based on ITO/GaP heterostructures are discussed. Such sensors have perfect electrical parameters and high UV-visible sensitivity in comparison with surface-barrier structures using a semitransparent thin metal film as an electrode. Many applications require UV sensors with an effective rejection of visible radiation and a wide temperature operating interval. For this aim, the theoretical modelling of extreme selective optical sensors with a double Ag/ITO thin film on the GaP surface, in which the thin silver film serves as a narrow bandpass filter at 320 nm, has been conducted. With this modelling the optimal thickness combination for the silver and ITO films was found for the maximum rejection of the sensitivity to visible radiation.

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA ELECTRÓNICA

Efficient ITO–Si solar cells and power modules fabricated with a low temperature technology: Results and perspectives

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE CARLOS ZUÑIGA ISLAS GUILLERMO RUIZ TABOADA (2008)

ITO–SiOx–nSi semiconductor–insulator–semiconductor (SIS) structures have been produced with a simple spraying technique. It is shown that the structures obtained in such a way may be considered as an induced p–n diode, in which the polycrystalline tin–doped indium oxide (ITO) layer spray deposited on the preliminary treated silicon surface leads to an inversion p-layer at the interface. Solar cells with an active area of 1–4 cm2 have been fabricated based on ITO–SiOx–nSi structures and studied. Under AM0 illumination conditions, the efficiency is nearly 11%, whereas it exceeds 12% for AM1.5 illumination conditions. The theoretical analysis provided in this work shows a good agreement with experimental results and allows for predicting the efficiency of the cells depending on the silicon electro-physical properties.

Article

Silicon Solar cells Photovoltaics Indium tin oxide and other transparent conductors CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA

Electrical characterization of a-C:H as a dielectric material in metal/insulator/metal structures

CARLOS ZUÑIGA ISLAS ANDREY KOSAREV ALFONSO TORRES JACOME PEDRO ROSALES QUINTERO WILFRIDO CALLEJA ARRIAGA FRANCISCO JAVIER DE LA HIDALGA WADE OLEKSANDR MALIK (2010)

The fabrication and electrical characterization of Metal- Insulator-Metal (MIM) structures, using a-C:H films as the insulating material, are presented in this work. These PECVD carbon films show a very low dielectric constant and a very high resistivity. The current conduction mechanisms were analyzed before and after the post deposition annealing in pure argon ambient at 400°C. For as-deposited films, the experimental J-U curves showed that under low biasing regime (|U| < 8 V) the space charge limited current conduction is the main transport mechanism, whereas under higher biasing regime (|U| > 8 V)) the current transport is dominated by the Schottky mechanism. For annealed structures, under low and high biasing the ohmic and Schottky mechanisms were identified as the main processes for the electrical transport. Finally, we found that both parameters, the dielectric constant and resistivity, decrease slightly after the thermal annealing.

Article

CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA ELECTRÓNICA