Влияние параллельного слоям магнитного поля на фототок в GaAs/AlAs p-i-n-структурах

The behavior of the photocurrent in GaAs / AlAs p-i-n heterostructures is studied in a magnetic field parallel to the heterolayers in the wavelength range from 395 to 650 nm. A strong dependence of the non-oscillating component of the photocurrent on the radiation wavelength associated with the suppression of the diffusion current by the magnetic field was found. It is shown that the behavior of the oscillating component of the photocurrent in a magnetic field does not depend on the wavelength of light and is determined by the transfer of electrons through the dimensional quantization level in a triangular near-barrier well. It is shown that the suppression of the oscillating component by the magnetic field is due to the smearing of the level in the triangular well due to the motion of electrons parallel to the walls of the well and perpendicular to the magnetic field.

Electrical properties of strained germanium nanofilm

Dependences of the concentration of intrinsic current carriers, electron and hole mobilities and specific conductivity for strained germanium nanofilms grown on the Si, Ge(0,64)Si(0,36) and Ge(0,9)Si(0,1) substrates with crystallographic orientation (001), on their thickness at different temperatures were calculated on the basis of the statistics of non-degenerate two-dimensional electron and hole gas in semiconductors. The electrical properties of such nanofilms are determined by the peculiarities of their band structure. It is established that the effects of dimensional quantization, the probability of which increases with decreasing temperature, become significant for germanium nanofilms with the thickness of d<7 nm. The presence of such effects explains the significant increase in the specific conductivity and the decrease in the intrinsic concentration of current carriers for these nanofilms. The electron and hole mobility in the investigated germanium nanofilms is lower in relation to such unstrained nanofilms. Only for the strained germanium nanofilm with the thickness of d> 50 nm grown on the Ge(0,9)Si(0,1) substrate, an increase in the hole mobility at room temperature of more than 1.5 times was obtained. The obtained results of the electrical properties of strained germanium nanofilms can be used in producing on their basis new elements of nanoelectronic.

Phonon spectrum of LED InGaN/GaN heterostructure with quantum wells

Measurements of the phonon spectrum of the LED heterostructure based on the In0.12Ga0.88N/GaN barrier showed the presence in it of four peaks of phonon radiation with energies of 0.193, 0.207, 0.353, and 0.356 eV. From a comparison of the results of the calculation of the energy spectrum of the electron and hole quantum wells with the obtained experimental data, it was assumed that these peaks can be interpreted as the energies of phonons generated during the capture of electrons from the barrier layer to the second level of dimensional quantization, as well as during the relaxation of electrons from the second level to the radiation level and trapping holes to the upper level of the quantum well.

FACE RECOGNITION TECHNIQUE FOR ATM SECURITY

In the recent decades the people are depending more on ATM machines for getting instant cash in anytime and anywhere. In related to these ATM machines are installing in every part of the country. As the ATM machines are growing, providing security level for ATM machines is the challenging factor. In the present days, ATM systems uses access card and PIN for identity verification. The technology advancement has bought different biometric identification technique like finger print, facial recognition and retina scanning. But still the security level is not compromising to customers. This model proposes a concept of providing two level security system in order to reduce the frauds like hacking of ATM cards, PIN stolen, Phishing attack etc., In this model Crypto-biometric system is adopted where biometric and cryptography are combined to achieve high security. Between face features and pairs of random vectors given by user, the two dimensional quantization of distance vectors process is used [1]. The cryptographic key generated is of 128 bits it is difficult for hacking. The merging of face features and random vectors are done by using MATLAB.

Electronic Structure and Itinerant Magnetism of Hydrogenated Graphene Nanofilms

The peculiarities of spin-polarized electronic structure of multilayer graphene nanofilm (4-GNL:H) within the framework of Kohn --- Sham approximation were studied in the present work. The calculated band structure and spin-resolved electronic energy spectrum of the 4-GNL:H system were correlated with experimental UPS and XANES spectra of thin hydrogenated a-C:H films. As the band structure calculations show there is a dimensional quantization of energy spectrum in the 4-GNL:H system, and the energy gap of 0.11 eV appears in the spectrum. The self-consistent calculations also predict the existence of itinerant magnetism in the system, conditioned by hydrogen chemisorption.