Águas, H.a, Goullet Pereira Fortunato Martins A. b L. a. "
Effect of the tunnelling oxide thickness and density on the performance of MIS photodiodes."
Thin Solid Films. 451-452 (2004): 361-365.
AbstractIn this work we present results of a study performed on metal-insulator-semiconductor (MIS) diodes with the following structure: substrate (glass)/Cr (2000 Å)/a-Si:H n+(400 Å)/a-Si:H i (5500 Å)/oxide (0-40 Å)/Au (100 Å) to determine the influence of the oxide passivation layer grown by different techniques on the electrical performance of MIS devices. The results achieved show that the diodes with oxides grown using hydrogen peroxide present higher rectification factor (2×106) and signal to noise (S/N) ratio (1×10 7 at -1 V) than the diodes with oxides obtained by the evaporation of SiO2, or by the chemical deposition of SiO2 by plasma of hexamethyldisiloxane. However, in the case of deposited oxides, the breakdown voltage is higher, 30 V instead of 3-10 V for grown oxides. The ideal oxide thickness, determined by spectroscopic ellipsometry, is dependent on the method used to grow the oxide layer and is in the range between 6 and 20 Å. The reason for this variation is related to the degree of compactation of the oxide produced, which is not relevant for applications of the diodes in the range of ±1 V, but is relevant when high breakdown voltages are required. © 2003 Elsevier B.V. All rights reserved.
Águas, H., Pereira Raniero Fortunato Martins L. L. E. "
Effect of the load resistance in the linearity and sensitivity of MIS position sensitive detectors."
Materials Research Society Symposium Proceedings. Vol. 862. 2005. 691-696.
AbstractIt is experimentally known that the linearity and sensitivity of the position sensitive detectors (PSD) are dependent on the resistance of the collecting layer and of the load resistance, mainly if the detection is based on the measurement of the photo-lateral voltage. To determine the value of the load resistance to be used in metal - insulator - semiconductor (MIS) PSDs structures that lead to the maximum value of sensitivity and linearity, we propose an electrical model through which it is able to simulate the proper sensor response and how the load resistance influence the results obtained. This model is valid for PSDs where the resistance of the collecting resistive layer is quite low (≤ 500 Ω), leading to a low output impedance. Under these conditions we conclude that the value of the load resistance should be of about 1 kΩ in order to achieve a good compromise between the linearity and the sensitivity of the PSD. This result is in agreement with the set of experiments performed. © 2005 Materials Research Society.
Águas, H., Raniero Pereira Fortunato Martins L. L. E. "
Effect of the discharge frequency and impedance on the structural properties of polymorphous silicon."
Thin Solid Films. 451-452 (2004): 264-268.
AbstractThis work presents a study performed on the deposition of pm-Si:H by plasma enhanced chemical vapor deposition using excitation frequencies of 13.56 and 27.12 MHz, where the interest of increasing the excitation frequency relies on higher plasma dissociation and reduced energy of ion bombardment, thus allowing the deposition of superior grade material at higher growth rates. The plasma impedance, which allows the monitoring of particle formation in the plasma, was correlated to the film properties, characterized by spectroscopic ellipsometry and hydrogen exodiffusion experiments. The set of data obtained show that by using the 27.12-MHz excitation frequency the hydrogen dilution and the r.f. power density needed to produce pm-Si:H can be reduced. Growth rates above 3.1 Å/s were obtained, the films being more dense and chemically more stable than those obtained with the standard 13.56 MHz. © 2003 Elsevier B.V. All rights reserved.
Dirani, E.A.T., Pereyra Andrade Soler Martins I. A. M. "
Effect of the deposition parameters on the electro optical properties and morphology of microcrystalline hydrogenated silicon alloys."
Conference Record of the IEEE Photovoltaic Specialists Conference. Vol. 2. 1990. 1588-1590.
AbstractMicrocrystalline phosphorus-doped hydrogenated silicon alloy films were deposited in a remote plasma CVD (chemical vapor deposition) system. The film properties were studied as a function of RF power density and hydrogen concentration in the reaction gas mixture. The properties of the deposited films are extremely sensitive to the RF power density in the studied range of 250 mW/cm2 to 625 mW/cm2. Very low values of electrical resistivity were obtained. For an RF power density of 500 mW/cm2, ρ = 3 × 10-2 Ω-cm, while ρ = 1.9 × 103 Ω-cm for 625 mW/cm2, indicating the predominance of the amorphous tissue over the microcrystalline phase. High doping efficiencies which can be correlated to large grain size are indicated by the very low values of the activation energy as low as 30 meV for 500 mW/cm2, that were obtained.