R. V. Konakova

Comparative characteristics of the Raman scattering spectra of graphene films on conductive and semi-insulating 6H-SiC substrates

The raman scattering (RS) spectra of graphene on semi-insulating and conductive 6H-SiC substrates formed by preliminary and additional annealing of silicon carbide at various temperatures are studied. The degree of perfection of the graphene films and sizes of its clusters are estimated. It is shown that the temperature of additional annealing in the case of conductive substrates should be higher than that for semi-insulating substrates to obtain graphene layers with the same structural perfection.

Characterization of field-emission cathodes based on graphene films on SiC

The properties of a point field-emission cathode representing a structure in the form of a silicon carbide tip coated with a thin graphene film are assessed. For the point cathode with the graphene coating, the current–voltage characteristics are constructed in the Fowler–Nordheim coordinates; the work functions φ of the point cathode are calculated by their slope. The possibility of forming heavily doped n+-SiC on the point surface by the sublimation of low-threshold field emission cathodes with low threshold electric fields and field-emission currents is shown.

Effect of microwave treatment on current flow mechanisms in Au-TiBx-Al-Ti-n+-n-n+-GaN-Al2O3 ohmic contacts

The temperature dependences of the contact resistivity ρc of Au-TiBx Al-Ti-n+-n-n+-GaN-Al2O3 ohmic contacts have been studied before and after microwave treatment followed by nine-nonth room-temperature sample storage. The temperature dependences of ρc of initial samples were measured twice. The first measurement showed the temperature dependence typical of ohmic contacts; the repeated measurement in the temperature region above 270 K showed a ρc increase caused by metallic conductivity. After microwave treatment, the metallic conductivity in the ohmic contact is not observed. This is presumably associated with local heating of metal Ga inclusions under microwave irradiation and the formation, due to high chemical activity of liquid gallium, of compounds of it with other metallization components. In this case, the temperature dependence of ρc is controlled by ordinary charge transport mechanisms. After nine-nonth room-temperature storage, the temperature dependence of ?c is described by the tunneling mechanism of charge transport.

Temperature dependences of the contact resistivity in ohmic contacts to n + -InN

The temperature dependences of the contact resistivity (ρc) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 1018 cm−3 in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρc(T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is ∼5 × 109 cm−2. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 1010 cm−2.

Effect of ultrasonic treatment on deformation effects and the structure of local centers in the substrate and in the contact regions of M/n−n+-GaAs structures (M=Pt, Cr, W)

The effect of ultrasonic treatment on the physicochemical, structural, and electrical properties of Pt, Cr, W/n-n+-GaAs structures has been studied. It is shown that the ultrasonic treatment produces spatial and chemical ordering of the contact GaAs region. This decreases the reverse currents in diode structures with a Schottky barrier. A possible mechanism of the effect of ultrasonic treatment on the structural and chemical reorganization in a M/n-n+-GaAs contact is discussed.

The influence of physical and chemical factors upon thermal and radiation stability of TiN-GaAs and TiB/sub 2/-GaAs contacts

It has been well established that degradation of metal-semiconductor structures in the course of their operation under extreme conditions (high temperatures, strong electromagnetic field, radiation, etc.) is crucially affected by the mass transfer processes and by the nature of solid-phase interactions between the pairs of layers forming the contact. Under the influence of external factors, the structural and phase composition of the interface boundary change, and similarly changes the degree of local non-uniformity, impurity and defect composition of the subsurface region of the semiconductors, which results, eventually, into variations (degrading) of the electric and physical properties of the contacts. Nowadays, the search for structures with contacts metal-A/sup 3/B/sup 5/ which are stable and resistant against external effects tends to examine such metallic alloys and compounds which could markedly weaken the interdiffusion of metal-semiconductor layers. Among them, of particular interest are titanium borides and nitrides. The paper present a comparative study of TiB/sub 2/(TiN)-GaAs structures.

Current flow through metal shunts in ohmic contacts to n +-Si

It is experimentally found that an ohmic contact based on Au-Pt-Ti-Pd-n+-Si metallization is formed due to nanoscale metal shunts containing Si, Au, and Pt in the region of the interface with n+-Si, which appears during heat treatment at T = 450°C for 10 min in a vacuum chamber with a residual pressure of 10−6 Torr. The high density of shunts adjoining dislocations and other imperfections is confirmed by the temperature dependence of the specific contact resistance ρc(T). The density of conductive dislocations, calculated from the temperature dependence of ρc is ∼5 × 109 cm−2 which correlates with the density of structural defects, determined by the etch pits after removal of the metallization layers.

Effect of rapid thermal annealing on the properties of ZrB/sub x/(TiB/sub x/)-Si contacts

We investigated heat tolerance of ZrB/sub x/-n-n/sup +/-Si and TiB/sub x/-n-n/sup +/-Si barrier contacts exposed to rapid (60 s) thermal annealing (RTA) in hydrogen atmosphere at T=400, 600, 800 and 950/spl deg/C. Using XPS, AES and static I-V curve measurements, we have shown that ZrB/sub x/-n-n/sup +/-Si(TiB/sub x/-n-n/sup +/-Si) contacts retain their layer structure and barrier properties after RTA at 950(600)/spl deg/C.

Ge-film resistance and Si-based diode temperature microsensors

New types of miniature temperature sensors based on Ge films and silicon diodes have been developed and produced. The Ge film microthermometers are intended for use at temperatures from 1 to 400 K, and silicon microdiodes cover operating temperature range from 1 to 600 K. The designs of sensitive elements and the miniature package, as well as sensor characteristics, are presented.

Nature of the transitional region during the deposition of titanium boride and nitride films on gallium arsenide

Photoluminescence and x-ray photoelectron spectroscopy methods were used to analyze the compositions of the near-junction regions of titanium boride (nitride)-gallium arsenide heterostructures. Data have been obtained for the first time on the formation of GaxB1−xAs and GaAsxN1−x solid solutions, which play an important role in the formation of the properties and the thermal stability of the experimental structures on the interphase boundary of these structures.