N.L. Dmitruk

Morphology and interfacial properties of microrelief metal–semiconductor interface

Abstract The effect of the morphology of Au/GaAs interface microrelief, prepared by chemical anisotropic etching, on current flow mechanism, electronic and recombination properties of interface has been investigated. Simulation of I – V curves and optical transmittance of light into semiconductor was made on the basis of the developed theories taking into account the barrier height distribution and the effect of scattering of light by low microrelief.

Modeling and measurement of optical response of 1D array of metallic nanowires for sensing and detection application

We have investigated 1D nanosized metallic wires with subwavelength dimensions in which localized surface plasmon (LSP) and surface plasmon polariton (SPP) can exist. Elaboration of the localized surface plasmon resonance (LSPR) based device for scaling down to nanometric dimensions, which provide significant flexible design is the aim of this paper. Modeling of the interaction of the incident light with the periodic system of nanowires (differential formalism) and measurements of the optical (transmittance, extinction) properties of the structures under consideration were performed to reveal the general trends in the design of the gold nanostructure geometry to optimize sensitivity of sensor system.

Texturized interface as a basis of surface-barrier heterostructure for solar cells application

Simulation of the photocurrent of surface-barrier structures (SBS) with texturized interface has been performed on the basis of obtained theoretical expression for internal quantum efficiency of homogeneous SBS and the model of parallelly connected diodes. The role of various sources of recombination losses (in the semiconductor, at the interface and due to the emission of majority carriers into the metal) in solar energy convertors has been analyzed. The complex method of characterization of SBS with texturized interface is proposed that includes an analysis of optical, electric and photoelectric characteristics. The possibility to increase the photosensitivity of the Au/GaAs SBS due to texturization and sulfur passivation of the interface for two types of microrelief (dendritic and quasigrating) obtained by wet anisotropic etching has been investigated. The morphology and statistical geometric characteristics of the interface were investigated by atomic force microscopy (AFM). The obtained results allowed to determine the change of optical and electronic (recombination) parameters of the interface caused by the used processing (texturization, passivation).

Analysis of thin film surface barrier solar cells with a microrelief interface

The influence of a microrelief interface between a thin conductive film (emitter) and a semiconductor substrate (absorber) on the optical and recombination losses in surface barrier solar cells is analyzed. Equations for the calculation of monochromatic light transmission through a thin absorbing film with one or two rough surfaces, on an absorbing substrate, are presented. For a weakly texturized interface and a normal direction of the incident light, the influence of the microroughness is taken into account by the formulae obtained. A model of patches with microsurfaces parallel to the structure surface and ones inclined to it at a certain angle (the most probable statistically) was used to describe the experimental results. Au/GaAs surface barrier structures with interface microrelief of a quasigrating or a dendritic type, obtained by chemical anisotropic etching of GaAs, were investigated. The geometric and statistical parameters of the microrelief were determined by atomic force microscopy techniques. The recombination parameters of the textured interfaces were determined from the experimental spectra of the external quantum efficiency, taking into consideration the calculated spectra of light transmittance. A comparison of the internal quantum efficiency spectra with the calculated ones allows a determination of the electronic parameters of the interface. Both the photoconversion parameters under AM0 simulated illumination and the tolerance for 60Co γ-irradiation, obtained for structures with various interface microrelief morphologies, allowed identification of microrelief of the quasigrating type as more suitable for solar cell applications.

Polarization-sensitive photocurrents of metal-semiconductor structures with flat and microrelief interfaces

Abstract The dependence of the polarization photosensitivity on parameters of a multilayer surface-barrier structure (SBS) (metal (Ag, Au) - intrinsic oxide - isotropic semiconductor (InP, GaAs)) with flat and microrelief interfaces has been studied. The influence of metal layer thickness on the polarimetric effect was analyzed. Both spectral and angular characteristics of the SBS polarization photosensitivity were calculated. Comparisons between the calculated angular characteristics of transmission coefficients for the light and those of the measured short-circuit photocurrent i ph for several wavelengths were made. To account for a micro-relief effect on the SBS polarization photosensitivity, the equivalent film method was used. The surface polariton excitation was shown to be an additional mechanism of photosensitivity enhancement and affected its polarization sensitivity.

Ultraviolet responsivity control in Schottky barrier heterostructures with textured interface

This paper is devoted to ultraviolet responsivity control in Schottky barrier heterostructures based on GaAs and InP with textured interface. The influence of microrelief morphology and of its geometrical parameters on optical properties and photoresponse characteristics (spectral and polarization) has been investigated. Both random microrelief obtained by chemical anisotropic etching of semiconductor and microrelief of grating type formed by holographic etching were used. The optical and photoelectric characterization of heterostructures with textured interface allowed us to determine the most promising type of microrelief, and to define the mechanisms of the photosensitivity enhancement. Specifically, the role of surface polariton excitation as a mechanism of photoresponse increasing was treated.

Effect of discontinuous gold films on GaAs-electrolyte contact properties

Abstract The morphology of a discontinuous gold film on a monocrystalline GaAs surface and its influence on the capacitance-voltage characteristics of a GaAs- electrolyte contact were studied experimentally. It was shown that, in the frequency and potential ranges studied, surface states do not manifest themselves at GaAs-Au and GaAs-electrolyte interfaces.

Effect of the interface on radiation defect formation in gallium arsenide

Abstract The problem of interface influence on the radiation defects formation in binary semiconductor compounds such as GaAs requires a complex studying as far as it is more complicated than in monoatomic ones (Ge, Si).

Influence of multilayer coating peculiarities on efficiency of surface plasmon resonance photodetector

A double metal layer system on the diffraction grating was used for increasing of efficiency of surface plasmon resonance (SPR) GaAs based photodetector. The design of it is based on commonly used thin metal films with optical constants that can be realized by using standard thermal evaporation techniques. The performance of detectors has been controlled over the wide range of visible spectrum by variation both geometric and structural parameters of diffraction grating. The sensitivity of the structures to changes in the angle of incidence, the wavelength, both the coating nature and index, etc. are presented.

Influence of modified surface of gaas on properties of heterostructures with organic semiconductors

The electrical, optical and photoelectric properties of organic/inorganic semiconductors heterostructures are investigated depending upon the interface microrelief morphology modified by chemical etching of GaAs. Polishing andanisotropic etchants were used to change it from flat to microtextured(quasigrating-type). The p/n-heterostructures were fabricated by the vacuumevaporation of thin (∼50 nm) pentacene or phthalocyanine of lead filmson modified surface of n-GaAs crystals. A considerable decrease of the optical reflectance and increase of the photosensitivity by a few (1.5-4) times have been obtained for microtextured heterostructures with respect to the flat ones.The results emphasize the importance of GaAs surface chemical microtexturing to future developments of the photocells, based on organic semiconductor/GaAs heterojunction.