G. Gonzalez Diaz

Deposition of SiNx : H thin films by the electron cyclotron resonance and its application to Al/SiNx : H/Si structures

We have analyzed the electrical properties and bonding characteristics of SiNx:H thin films deposited at 200 °C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio N/Si<1.33) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between N/Si=1.1 and 1.4, hydrogen concentration remains below 10 at. %. The films with N/Si=1.38 exhibited the better values of the electrical properties (resistivity, 6×1013 Ω cm; and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on n-type silicon wafers. C–V measurements accomplished on the structures indicate that the interface trap density is kept in the range (3–5)×1011 cm−2 eV−1 for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.4, the trap density suddenly ...

Structural, electrical, and optical properties of CuGaSe2 rf sputtered thin films

Thin films of CuGaSe2 have been produced by rf sputtering. Compositional, structural, electrical, and optical properties are strongly influenced by growthtemperature. At substrate temperatures lower than 300 °C amorphous or poorly crystalline Se‐excess films are obtained, showing high resistivity (≊103 Ω cm) and optical transitions at 1.62, 1.80, and 2.4 eV (values lower than the single‐crystal counterparts). At the higher growthtemperatures,polycrystalline films are obtained (average grain size 0.7 μm) with lower values of resistivity (1 Ω cm), and optical transitions at 1.68, 1.90, and 2.55 eV (very close to the single‐crystal values). A hopping conduction mechanism has been detected at the lower measuringtemperature (T 150 K). Structural and compositional characteristics are used to explain the behavior observed in the electrical and optical properties.

Rapid thermally annealed plasma deposited SiNx:H thin films: Application to metal-insulator-semiconductor structures with Si, In0.53Ga0.47As, and InP

We present in this article a comprehensive study of rapid thermal annealing (RTA) effects on the physical properties of SiNx:H thin films deposited by the electron cyclotron resonance plasma method. Films of different as-deposited compositions (defined in this article as the nitrogen to silicon ratio, x=N/Si) were analyzed: from Si-rich (x=0.97) to N-rich (x=1.6) films. The evolution of the composition, bonding configuration, and paramagnetic defects with the annealing temperature are explained by means of different network bond reactions that take place depending on the as-deposited film composition. All the analyzed films release hydrogen, while Si-rich and near-stoichiometric (x=1.43) ones also lose nitrogen upon annealing. These films were used to make Al/SiNx:H/semiconductor devices with Si, In0.53Ga0.47As, and InP. After RTA treatments, the electrical properties of the three different SiNx:H/semiconductor interfaces can be explained, noting the microstructural modifications that SiNx:H experiences upon annealing.

Good quality Al/SiNx:H/InP metal-insulator-semiconductor devices obtained with electron cyclotron resonance plasma method

We have obtained Al/SiNx:H/InP metal-insulator-semiconductor devices depositing SiNx:H thin films by the electron cyclotron resonance plasma method at 200 °C. The electrical properties of the structures were analyzed according to capacitance–voltage and deep level transient spectroscopy measurements. We deduce an inverse correlation between the insulator composition—the N/Si ratio—and the density of interface traps: those films with the maximum N/Si ratio (1.49) produce devices with the minimum trap density—2×1012 cm−2 eV−1 at 0.42 eV. above the midgap. We explain the influence of film composition on the interface trap density in terms of a substitution of phosphorous vacancies at the InP surface, Vp, by N atoms coming from the insulator, NVp. The values obtained in our research for the interface trap distribution were similar to other published results for devices that use chemical and/or physical passivation processes of the InP surface prior to the deposition of the insulator.

Role of deep levels and interface states in the capacitance characteristics of all‐sputtered CuInSe2/CdS solar cell heterojunctions

All‐sputtered CuInSe2/CdS solar cellheterojunctions have been analyzed by means of capacitance‐frequency (C‐F) and capacitance‐bias voltage (C‐V) measurements. Depending on the CuInSe2 layer composition, two kinds of heterojunctions were analyzed: type 1 heterojunctions (based on stoichiometric or slightly In‐rich CuInSe2 layers) and type 2 heterojunctions (based on Cu‐rich CuInSe2 layers). In type 1 heterojunctions, a 80‐meV donor level has been found. Densities of interface states in the range 101 0–101 1 cm2 eV− 1 (type 1) and in the range 101 2–101 3 cm− 2 eV− 1 (type 2) have been deduced. On the other hand, doping concentrations of 1.6×101 6 cm− 3 for stoichiometric CuInSe2 (type 1 heterojunction) and 8×101 7 cm− 3 for the CdS (type 2 heterojunction) have been deduced from C‐Vmeasurements.

Determination of the dark and illuminated characteristic parameters of a solar cell from I-V characteristics

The authors present a systematic procedure to obtain the main parameters which characterize a commercial solar cell, both in dark conditions (series and shunt resistances and recombination and diffusion saturation currents) and also under illumination (short circuit current, open circuit voltage and fill factor). All the measurements needed are made with simple and inexpensive apparatus and the calculations are straightforward. Throughout the work the didactic aspect of the experiments was kept in mind. The common approximation of using a single exponential term with a diode factor n (different from 1 or 2) to describe the junction behaviour is not appropriate even using common laboratory multimeters if the measurements are taken carefully.

Sputtering of SiO2 in O2Ar atmospheres

Abstract The r.f. sputtering of SiO 2 in an ArO 2 atmosphere was studied. The study was carried out to improve the insulating properties of films relative to those produced in a pure argon discharge which showed a clear aging effect on the losses. The O 2 percentage was varied in the range 1%–4% of the total pressure. The improvement in the insulating properties consisted mainly in a stabilization of the electrical properties close to the best values reported for SiO 2 . The role of the oxygen is explained on the basis of annihilation of defects associated with oxygen vacancies in the SiO 4 tetrahedral chains.

The influence of film properties on the electrical characteristics of metal - insulator - semiconductor devices

thin films were deposited by the electron cyclotron resonance plasma method at low substrate temperature (C) to fabricate metal - insulator - semiconductor devices. The effects of film properties on the electrical characteristics of two different devices, and , were analysed according to the C - V high - low frequency method. The results show that, in the devices based on Si, the presence of N - H bonds in the film increases the density of trapping centres at the insulator/semiconductor interface. This behaviour was analysed by the model recently proposed by Ying (1995 J. Vac. Sci. Technol. B 13 1613) for nitrided interfaces. For the capacitors, the electrical characteristics of the interface were strongly dependent on the composition. When the nitrogen to silicon ratio of the film was , the minimum of the interface trap density was . This value was similar to the same data reported by other authors on devices where the InP surface was sulphur passivated. This suggests that nitrogen atoms of the insulator play some passivation role at the InP surface. The plasma exposure of the semiconductor surface during the deposition of the film promotes the formation of phosphorus vacancies at the InP surface. Nitrogen atoms may fill these vacancies and this gives rise to an insulator/semiconductor interface with few defects.

Analysis of light-emission processes in light-emitting diodes and semiconductor lasers

We present a laboratory experiment to show the current - voltage (I - V), light output - voltage (L - V) and light output - current (L - I) characteristics of light-emitting diodes (LEDs) and semiconductor laser (SLs). The experiment allows us to compare the processes of light emission in LEDs and lasers below the threshold (spontaneous emission) and above it (stimulated emission). We establish unambiguously the analogies of the characteristics of LED emission in comparison with laser emission, when this occurs in the regime of spontaneous emission. We also determine the differences between LED and laser operation (when this occurs in the regime of stimulated emission) in a different way than that usually found in textbooks. Resumen. En este trabajo se presenta un sistema experimental destinado a mostrar las relaciones entre las caracteristicas I - V, L - V y L - I de diodos emisores de luz (LED) y laseres de semiconductor. La experiencia permite comparar los procesos de emision de luz de los LEDs y laseres por debajo del umbral (emision espontanea) y por encima de el (emision estimulada). Mostramos de forma clara las analogias entre el LED y el laser en la zona de emision espontanea. Cuando el laser trabaja en la zona de emision estimulada, las diferencias se caracterizan de forma distinta a la habitual de los libros de texto.

Improvement of SiNx:H/InP gate structures for the fabrication of metal–insulator–semiconductor field-effect transistors

In this paper we report on the optimization of the SiNx:H insulator, deposited by the electron cyclotron resonance (ECR) plasma method, as a dielectric for metal–insulator–semiconductor (MIS) structures built on an InP compound semiconductor. Two different MIS structures have been obtained in which the minimum of the interface trap density (Dit,min) at the insulator/InP interface attains values of device quality. In the first structure, a Al/SiN1.5:H/SiN1.6:H/InP dual-layer insulator was obtained and optimized after rapid thermal annealing treatment at 500 °C for 30 s. After this treatment, the value of Dit,min was 9 × 1011 cm−2 eV−1. In the second structure, the MIS structure was Al/SiN1.6:H/InP single-layer insulator, in which the InP surface was exposed to an N2 plasma prior to the SiN1.6:H film deposition. In this case, the value of Dit,min was 1.6 × 1012 cm−2 eV−1. Both types of structures were used as gate insulators on N-channel enhanced-mode MIS field-effect transistor test devices. From the dc output characteristics of the transistors, we obtain values for the electron channel mobility in the range 1550–1600 cm2 V−1 s−1. This is a confirmation of the great potential of the ECR plasma method as a simple way to obtain device quality gate structures on InP without the use of passivation processes of the InP surface prior to the deposition of the gate dielectric, thus simplifying the whole device fabrication procedure.