L. A. Matveeva

Growth of III–V semiconductor layers on Si patterned substrates

Abstract Patterned unheated Si{100} substrates in the form of the regular tetragonal pyramids and a structure like hemispherical plates have been found to be effective for a pulse vacuum thermal deposition (pulse-VTD) of GaAs and GaP thin layers (50–500 nm). The effect of the pulse-VTD technological parameters (pulse duration, pulse period, pulse number, pulse current) and the features of the substrate patterns (terraces, steps, kinks, sponges) on the morphology, the composition and the crystallinity of GaAs and GaP layers have been characterized by scanning electron microscopy, electron X-ray analysis and electron diffraction.

Microwave-stimulated relaxation of internal strains in GaAs-based device heterostructures

We have studied the effect of microwave radiation (frequency, 2.45 GHz; specific power density, 1.5 W/cm2) on the relaxation of internal mechanical strains in the (i)n-n+-GaAs structures, (ii) Au-Ti-n-n+-GaAs diode structures with Schottky barriers, and (iii) GaAs-based Schottky-barrier field-effect transistors (SFETs). It is shown that exposure of the samples to the microwave radiation for a few seconds leads to relaxation of the internal mechanical strains and improves the quality of the semiconductor surface layer structure. This results in improved parameters of the GaAs-based device structures of both (diode and SFET) types, as manifested by increased Schottky barrier height, reduced ideality factor and back current in the diode structures, and increased gain slope and initial drain current in the SFETs.

Effect of the Si wafer pretreatment on the patterned substrate morphology and growth of Hg1−xCdxTe PLD films

Silicon patterned substrates and Hg 1-x Cd x Te films prepared by pulse laser deposition (PLD) on these substrates were examined by scanning electron microscopy (SEM), electronography (EG) and low-field electroreflectane (ER) spectroscopy in dependence on a pretreatment of Si wafers and the microrelief type. Change in morphologies of the substrates and films is discussed. The crystallinity data and analysis of ER spectra parameters are presented.

Probe microanalysis investigation and electroreflectance spectroscopy of Hg1−xCdxTe PLD films on silicon patterned substrates

Abstract Hg1−xCdxTe films were prepared on Si-patterned substrates by the pulse laser deposition technique from a Hg1−xCdxTe target (x≈0.2). The effects of different substrate temperatures, ranging from 293 to 543 K, different laser shots number in the range of 10–380, and the morphological type of the patterned substrate on the x-composition of films were studied by electron probe microanalysis (EPMA) and electroreflectance (ER) spectroscopy. The correlation between a film composition measured by EPMA and one determined from ER spectra data was observed.

The Influence of Carbon on the Properties of Si/SiGe Heterostructures

Si/SiGe/SiGe:C/SiGe/Si heterostructures are investigated by Raman spectroscopy, electroreflectance method, and secondary-neutral mass spectrometry. It is shown that doping of a SiGe layer lying between undoped SiGe layers with C (1.5%) leads to almost complete stress relaxation in the doped layer. It is found that high-temperature photon annealing is responsible for a partial stress relaxation in the lower SiGe buffer layer. However, such annealing increases the Si content in this layer. Low-temperature treatment in the radio-frequency (RF) hydrogen plasma leads to considerable stress relaxation in the lower buffer layer without varying its composition. The results obtained from the electroreflectance and secondary-neutral-mall spectra correlate with the Raman spectroscopy data.

Structural-phase ordering in Ta/sub 2/O/sub 5/-p-Si heterosystem enhanced by microwave processing

We present the results of comprehensive investigations of the effects of ordering enhanced by magnetron microwave radiation (frequency of 2.45 GHz, irradiance of 1.5 W/cm/sup 2/, and processing duration of 10 s) in Ta/sub 2/O/sub 5/-p-Si heterosystem and MIS structures with Ta/sub 2/O/sub 5/ insulator 16-24 nm thick. It was shown that using microwave treatment of investigated samples we can receive practically relaxed heterosystems whose parameters correlate with characteristics of MIS structures. In this case the Ta/sub 2/O/sub 5//p-Si interface becomes essentially ordered.

Electroreflectance of porous layers obtained by stain etching of laser modified silicon

Optical properties of an SiOx porous silicon (PS) interface, prepared by stain etching of the laser modified p-Si surface, were investigated. The electroreflectance spectra (ERS) were measured in the region of 3.0-3.8 eV. A correlation between the existence of photoluminescence (PL) and the polarity inversion of the ERS signal of PS, compared to the laser modified Si or PS samples without PL, is established. It is shown that PL appears due to the electron enrichment of the near interface region caused by the positive charge imbedded into the oxide layer. The transition energy experiences a red shift with the increasing thickness of the oxide film. The intrinsic field between the oxide layer and Si increased with the ageing of the PS samples displaying PL. The results obtained support the surface localization model of PS PL controlled by the tunnelling mechanism of photocarriers through the Si/SiOx barrier.

The influence of hydrogen plasma on the electroreflectance spectrum and the spectrum of electron states of porous silicon

Porous Si samples were investigated by the electroreflectance modulation spectroscopy. The presence of minibands, which are responsible for the existence of photoluminescence bands (red, green, and blue), is revealed. It is established that the miniband responsible for the blue band vanishes upon the treatment of a porous Si surface in H+ plasma. Passivation of the surface with hydrogen also leads to strain relaxation both in porous films and in the Si substrate. The origin of electron states in the band gap of Si nanocrystallites is established.

Nanotechnology, features of surfaces and interfaces in the nanostructures with C 60 fullerenes and carbon composite films

Nanostructures with C60 fullerene and carbon composite film were obtained by thermal sublimation in vacuum of microcrystalline C60 powder onto non heated silicon and cover glass substrates. With increasing deposition rate of fullerenes, they decayed during the growth of the film. Surface and interface of nanostructures were studied using Raman scattering, atomic force microscopy and the modulation spectroscopy method of the electroreflectance. We have found that the deposition rate of the C60 molecular beam strongly influences on the composition of the films, their crystalline structure and surface morphology. Franz-Keldysh and surface quantum-size effects were observed in nanostructures with fullerenes. The value of the built-in electric field, the energy of the quantum levels and the width of surface quantum well, depending on the heterosystems manufacturing technology, were determined. In heterosystems with carbon films these effects were absent.

Effect of microwave irradiation on the resistance of Au-TiB x -Ge-Au- n - n + - n ++ -GaAs(InP) ohmic contacts

Temperature dependences of the contact resistivity ρc of Au-TiBx-Ge-Au-n-n+-n++(GaAs)-InP ohmic contacts before and after short-term (10 s) microwave treatment have been studied both experimentally and theoretically. It is shown that ρc can decrease after microwave treatment in the entire temperature range of ρc measurements (100–400 K). Good agreement between the theoretical and experimental ρc(T) curves is attained and interpreted on the assumption that the dislocation density in the semiconductor near-surface region is varied as a result of microwave radiation.