M. Shamsuddin

Electrical characterization of interface states in Ni/n-Si(111) Schottky diodes from (C-V) characteristics

Abstract Experiments have been performed on Ni/n-Si(111) Schottky diodes fabricated by the vacuum vapor deposition of Ni at ∼10−5 Torr pressure on an n-type «111a oriented silicon wafer. Measured current-voltage and capacitance-voltage characteristics in range frequency range 10 kHz-1 MHz have been analysed. Interface states parameters have been extracted from ( C-V ) characteristics using a metal-thin interfacial layer-semiconduct (MIS) structure model. The interface states density has been found to be in the range of 1011 cm−2 eV−1 with a peak in the band gap of Si at about 0·51 eV below the conduction band edge.

On the electrical conductivity of thermally evaporated CdS thin films

Cadmium sulphide (CdS) plays an important role in the development of thin-film photovoltaic devices [1‐5]. Hetrojunctions of CdS and other semiconductors such as CdTe, Cu2S, CuInSe2 and InP etc. have excited interest and made it possible to have efficient thin film solar cells. Low resistive CdS films are used in hetrojunctions in solar cells to lower the cell series resistance, whereas high resistive films are used for surface acoustic wave devices. The optimization of device characteristics requires a better understanding of the transport properties of these films. Electrical conductivity measurements are widely used in the characterization of transport properties of thin films [6‐8]. It has been established that the boundaries between grains in the polycrystalline films play an important role in determining the conductivity of the films [9‐11]. Many workers have grown CdS thin films using different deposition techniques such as thermal evaporation, spraying, chemical vapor deposition, sputtering etc. In this paper we report the electrical conductivity measurements of CdS thin films prepared by thermal evaporation. High purity (99.999%) cadmium and sulfur obtained from Johnson and Matthey (U.K.) were used in this investigation. An intimate mixture (8.01255 gm) of fresh powders of cadmium (150 µm) and sulfur (100 µm) in stoichiometric proportion corresponding to the composition CdS was placed in the graphite crucible. The crucible was kept in a transparent silica tube which after evacuation and insertion of argon (with oxygen impurity less than 2 ppm) was heated at a constant and reproducible rate of 3 K/min by a Thermal Program Controller (Make: ULVAC, Sinku Riku, Japan; Model: HPC-7000). The temperature of the sample was maintained constant at 900 K for 2 h and then heated again up to 1250 K at a rate of 5 K/min. It was held at 1250 K for 24 h and then furnace cooled to room temperature. The CdS sinter was taken out and ground into powder in a mortar and pestle. The formation of the compound was confirmed by X-ray powder diffraction patterns. Rectangular films (5 cm × 1.5 cm) of CdS varying in thickness from 1000 ˚

On the study of electrical conductivity of polycrystalline cadmium telluride

The complex impedance of polycrystalline cadmium telluride has been measured as a function of frequency by a two-probe technique. The experimental data measured in the temperature range 301–565 K have been analyzed in the complex plane formalism and suitable equivalent circuits have been proposed in different temperature regions. The values of resistance and capacitance of bulk and grain boundary contributions have also been independently calculated from the Debye peak of spectroscopic plots. The role of bulk and grain boundary in the overall conduction process have been discussed with realistic justification.

Effects of hydrogenation on the electrical characteristics of Ni/n-Si(111) Schottky diodes

Abstract Hydrogenation effects on the electrical characteristics of Ni/n-Si(111) Schottky diodes have been reported from (I-V) and (C-V) studies. It has been concluded that hydrogen lowers the work function of nickel and also generates interfacial traps at the SiSiO2 interface. Slight passivation of deep donor states responding to the lower frequency test signal has also been observed after hydrogenating the diode.

Electrical characterization of semiconducting polycrystalline GaxIn(1−x)Sb alloys

The electrical conductivity, Hall coefficient and mobility of the sintered pellets of semiconducting polycrystalline GaxIn(1−x)Sb alloys (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.8 and 1) have been determined in the temperature range 290–425 K. The variation of d.c. electrical conductivity with temperature has been explained by Setos model. Samples withx=0.5 and 0.7 have been found to show anomaly in Hall effect sign, while the sample withx=1, i.e. GaSb, shows a Hall effect too small to be detected. Various kinds of scattering mechanisms under different temperature ranges have been observed in different alloy samples.

Hydrogenation effects on Ni/n-Si(111) Schottky diode characteristics

Experiments have been performed on Ni/n-Si(111) Schottky diodes fabricated by the thermal vacuum deposition of nickel on n/n+ Si epitaxial wafers at approximately 10-5 torr pressure. (I - V) and (C - V) characteristics have been measured at different frequencies in the range 10 KHz-1 MHz. Hydrogenation effects on the diode characteristics have been reported from (I - V) and (C - V) studies. It has been found that hydrogen lowers the work function of nickel and also generates the interfacial traps at the Si- SiO2 interface. These results are found in agreement with the results based on transient capacitance response and (C - V) studies. Slight passivation of deep donor states responding the low frequency test signal has also been observed after hydrogenating the diode. Interface states parameters have been extracted from (C - V) characteristics using the metal-interfacial layer semiconductor (MIS) structure model.