Search results

The purpose of this paper is to study the structural and optical characterization of Al_x In_y Ga_1−x−y N quaternary epilayers, which were grown on c‐plane (0001) sapphire substrates with AlN as buffer layers using plasma assisted molecular beam epitaxy technique with indium (In) mole fraction y ranging from 0.0 to 0.1 and constant aluminum (Al) mole fraction x=0.06.

High‐resolution X‐ray diffraction rocking curve (HRXRD‐RC), scanning electron microscopy (SEM), energy dispersive X‐ray spectrometry (EDX), and photoluminescence (PL) spectroscopy have been measured on quaternary Al_x In_y Ga_1−x−y N thin films at room temperature.

HRXRD‐RC measurements confirmed that the Al_x In_y Ga_1−x−y N alloys had wurtzite structure. SEM images, element composition analysis by EDX, provided the evidence to show the existence of defects inside the samples contaminated by silicon from previous growth leading to nonuniformity of the epilayers, which caused decreased in the quality of the samples. PL spectra show reducing of the integrated intensity and an increasing red shift with increasing in content with reference to the ternary sample Al_0.06Ga_0.94N. The existence of a large amount of nonradiative recombination centers are responsible for the reduced the luminescence and the red shift provided evidence to an increase in composition inside the Al_x In_y Ga_1−x−y N quaternary alloys. Photoluminescence is used to determine the behavior of the near band edge emission represent the energy band gap of the quaternary films. The energy band gap decreases with increasing In composition from 0.01 to 0.1 mole fraction. This trend is expected since the incorporation of in reduced the energy band gap of ternary Al_0.06Ga_0.94N (3.529 eV). We have also investigated the bowing parameter of the variation of energy band gaps and found it to be very sensitive on in composition. A value of b=10.95 have been obtain for our quaternary Al_x In_y Ga_1−x−y N alloys.

This study on quaternary samples described in this paper, clearly indicates that the present of defects due to impurity contaminations has a dominant role in determining the structural and optical properties of Al_x In_y Ga_1−x−y N quaternary alloys.

The purpose of this paper is to: analyze the changing properties of epitaxial layers, manufactured in the considered reactor, with the changing parameters of the growth taking into account native convection; and development of the most common analytical approach to describe the technological process.

In this paper a vertical reactor for gas phase epitaxy is considered that consists of an external casing, a keeper of substrate with a substrate and a spiral around the casing in area of the growth zone to generate induction heating in order to activate the chemical reactions in the decay of reagents and the growth of the epitaxial layer by using the reagents. The authors introduce an analytical approach to analyze nonlinear mass and heat transport with account variation in space and time parameters.

The authors find conditions to improve properties of epitaxial layers.

Growth regimes at atmospheric and low pressure have been compared and analyzed for their influence of the native convection on the growth of the epitaxial layers. Accounting for the calculated results, recommendations have been formulated to improve the properties of the epitaxial layers.

The purpose of this paper is to present a novel n‐buried‐PSOI sandwiched radio frequencies (RF) power lateral diffused metal‐oxide semiconductor (LDMOS) and analyze its output characteristics.

The small‐signal equivalent circuit for RF power LDMOS method is used to analyze the proposed structure and the simulation and optimization are done using the computer‐aided design tools.

This improved structure is clearly decreasing drain‐substrate parasitic capacitance. At 1 dB compression point, its output power, the power‐added efficiency and the breakdown voltage are higher than that of the conventional LDMOS.

This paper puts forward a novel n‐buried‐PSOI sandwiched structure of RF power LDMOS. The analysis indicates that the output characteristics of this device are a great improvement on the conventional LDMOS and the n‐buried‐PSOI, RF power LDMOS proposed by earlier authors.

In this paper the MOPIT system for the simulation of devices and manufacturing processes is presented. The MOPIT system is meant for the simulation of the following semiconductor processing : ion implantation of impurities , diffusion , radiation enhanced diffusion , thermal oxidation of silicon , molecular‐beam epitaxy, plasma‐chemical etching and deposition, cross‐sectional profile evolution of trench in plasma‐etching and deposition; as well as the following devices: MOS‐structures , high‐voltage diode, element of memory, charge accumulation in a sub‐gate dielectric.

This paper aims to report on the use of radio frequency nitrogen plasma‐assisted molecular beam epitaxy (RF‐MBE) to grow high‐quality n‐type In_0.47Ga0.53N/GaN on Si(111) substrate using AlN as a buffer layer.

Structural analyses of the InGaN films were performed by using X‐ray diffraction, atomic force microscopy, and Hall measurement. Metal‐semiconductor‐metal (MSM) photodiode was fabricated on the In_0.47Ga0.53N/Si(111) films. Electrical analysis of the MSM photodiodes was carried out by using current‐voltage (I‐V) measurements. Ideality factors and Schottky barrier heights for Ni/In_0.47Ga0.53N, was deduced to be 1.01 and 0.60 eV, respectively.

The In_0.47Ga0.53N MSM photodiode shows a sharp cut‐off wavelength at 840 nm. A maximum responsivity of 0.28 A/W was achieved at 839 nm. The detector shows a little decrease in responsivity from 840 to 200 nm. The responsivity of the MSM drops by nearly two orders of magnitude across the cut‐off wavelength.

Focuses on III‐nitride semiconductors, which are of interest for applications in high temperature/power electronic devices.

With the advent of sophisticated growth techniques such as Molecular Beam Epitaxy and Metal Organic Chemical Vapor Deposition, the calculation of the energy boundstates and electron wave‐functions of the one‐electron Schrödinger equation has received a lot of attention over the last decade. With the more recent fabrication of quantum wires and dots, it seems now imperative to extend the boundstates calculation to systems containing only a few electrons. Hereafter, we investigate the effect of electron exchange and Coulomb interactions on the boundstates of a two‐electron system in a square quantum well. The technique is based on a general Alternating Direction Implicit algorithm ( T. Singh and M. Cahay, SPIE Vol. 1675, Quantum Wells and Superlattice Physics IV (1992), p.11) combined with a Fourier spectrum analysis of the two‐particle wavefunction correlation , <ψ(χ1,χ2;0)/ψ(χ1,χ2;τ)> , where χ1, χ2 are the coordinates of the two electrons. The precise location of the energy eigenvalues requires the appropriate use of window functions before calculating the Fourier transform of the correlation function. We also compare our results for the boundstate energies with those obtained using a first order time‐independent perturbation theory.

Optoelectronic components such as lasers and avalanche photodiodes have already revolutionised long distance transmission, and yet the technology is still in its infancy. Future generations of optoelectronic components will see the increasing integration of electronic, optoelectronic and optical functions on single chips, bringing about dramatic improvements in performance and the lower costs that will be required for widescale introduction of broadband networks and services.

THE element silicon (Si) has attained a dominant position in the field of manufacturing micro‐electronic components. This dominant position is due to properties which will perhaps assume even greater significance in the future. Silicon is universally applicable both for sensors, and for analogue and logic circuits as well as for memory cells. It is comparatively easy to work with. It is completely non‐toxic, and is therefore environmentally harmless. Supplies of silicon are almost limitless; after oxygen silicon is the second most common element in the earth's crust. Silicon crystallises in a diamond lattice (Fig. 1). Its universal applicability as a semiconductor is not synonymous with the optimal suitability for the current special application. The most far‐reaching proposal for overcoming the inadequacies of natural semiconductors came from L. Esaki. A superlattice structure (Fig. 2) is produced by arranging alternate layers of different elements. The atoms A and B are arranged periodically with a period length which superposes the natural period of the lattice. If the period of the superlattice is small (e.g. 3 to 100 atomic layers) new properties would be expected, which arise from the mixed crystals (synthetic semiconductor). The properties of the synthetic semiconductor are controllable by the geometrical dimensions and the concentrations of the superlattice structure.

The paper aims to provide a technical review of the application of quantum dot (QD) technology to sensors.

Following a brief introduction to QD technology, this paper considers recent research on QD‐based physical, chemical and gas sensors.

This shows that QDs are being exploited in a range of experimental sensors for detecting physical variables, notably radiant/electromagnetic quantities and temperature; chemical compounds, such as metals and many species of clinical interest; and a variety of gases and vapours. Prospects also exist to develop improved sources and detectors for use in optical gas sensors.

The paper does not consider biomedical uses of QDs such as cellular imaging, bioassays and biosensors.

This provides a detailed insight into recent research on physical, chemical and gas sensors based on QD technology.

Describes the key attributes of MEMS technology and existing and future business opportunities. Discusses the various stages in the fabrication of MEMS devices and offers guidance regarding the selection of processing methods for deposition, lithography and etching. Also describes the MEMS‐Exchange program and associated network of fabrication centres.