Aleksander V. Voitsekhovskii

Radiation effects in photoconductive MCT MBE heterostructures

The first results on a radiation stability investigation of mercury cadmium telluride (MCT) films, grown by molecular beam epitaxy (MBE) are represented. The samples were irradiated by high energy electron beams and gamma rays. Electrophysical and photoelectric parameters of MCT epilayers were measured. Volume material was measured too for the checking with MBE-grown one. MBE epifilms were irradiated on a pulsed electron accelerator with electron energy 1-2 MeV and current density less than 1 μA/cm2 for several fluences. Also MCT epitaxial heterostructures were irradiated by Co60 gamma rays. The same experiments were carried out for volume material. The analysis of dependence of Hall coefficient and conductivity from temperature and magnetic field (B) for p- and n- type samples was made. The irradiation of epilayers and volume MCT in the investigated range of irradiation fluences does not give both creation of electrical active damages in high concentrations and reconstruction of initial defects. Thus, MBE films of MCT have the high radiation stability to an electron and gamma irradiation. The obtained first results allow us to speak about high performance of explored MCT epilayers.

Photoelectric characteristics of inhomogeneous MIS structures based in Si, HgCdTe

The abnormal photoelectric properties of MIS structures, such as a significant photo-emf signal in the state of enhancement and a drop of the local photo-emf in inversion, were investigated with integrated and local photoelectric measurements. It has been established that the reason for the significant photo-emf signal in enhancement and the related features of the photoelectric properties of the structure is the photosensitivity in the region away from the electrode associated with a nonuniform distribution of electrically active defects. It has been demonstrated that the nonuniformity in surface potential (between the subelectrode region and the region away from the electrode (after-electrode region) or between different points in subelectrode region) may result in a drop of the local photo-emf in inversion. A conclusion has been made that the redistribution of nonequilibrium carriers along the boundary must be taken into account in constructing equivalent circuits of actual MIS structures.

Spectral detectivity and NETD of doping-spike PtSi-p-Si and HIP GeSi-Si detectors

Platinum silicide Schottky barrier detectors (SBD) and HIP-detectors GeSi/Si-based are widely used for application in the infrared spectral range. The increase in cutoff wavelength and responsivity of PtSi-Si photodevices is possible by formation of heavily-doped thin layer near to the semiconductor surface. The cutoff wavelength of HIP-detectors GexSi1-x/Si-based depends on x and concentration of boron in GeSi. In this report, the threshold properties of these detectors are considered. The dependencies of spectral detectivities and NETD from cutoff wavelength are calculated for various parameters of SBD and HIP-detectors. It is shown that optimal NETD of a SBD and HIP-detectors is possible for certain cutoff wavelength and temperature of detectors and depends on storage capacity. Also opportunity of formation of heavily-doped nanolayer in SBD detectors used by short-pulse recoil implanation of boron was studied.

Photoelectric characteristics of PtSi-Si Schottky barrier with heavily boron-doped nanolayer

The photo electric characteristics of Schottky barriers, created by recoil implantation in silicon, are analyzed. Implantation of boron atoms in silicon samples was made by recoil method, inducing Al ion beams bombardment, with current density 4-10 A/cm2 and 30-150keV energy. A SIMS analysis of obtained structures and calculation of their electric parameters show the opportunity of conducting layers formation, with a thickness of 10 nm and carrier concentration higher than 1018 cm-3.

Photoelectric properties of inhomogeneous infrared MIS photodetectors in base of HgCdTe and Si

The abnormal photo electric properties of MIS structures in base of Si and HgCdTe, such as a significant photo-emf signal in enhancement and drop of the local photo-emf in inversion, were experimentally investigated. It has been established that the reason for the significant photo-emf signal in the state of enhancement and the related features of the photo electric properties of the Si-MIS-structure, is the photosensitivity in the region far from the electrode, associated with non-uniform distribution of electrically active defects in this region. It has also been established that the non-uniformity in surface potential (between the sub-electrode region and the region away from the electrode or between different points in sub-electrode region) may result in a drop of the local photo-emf in the state of inversion. A conclusion has been made that the redistribution of non-equilibrium carriers along the boundary must be taken into account in constructing equivalent circuits of the MIS structures.

Investigation of MIS-structures on MnxHg1-xTe

We inform on results C-V measurements of structures metal- insulator MnHgTe, in which interface insulator-MnHgTe is created anodic oxidation. Results of researchers of a structure of distribution of elements of a matrix on interface by a method Rutherford backscattering spectrometry are submitted. Interrelation between the characteristics of interface and C-V characteristics is shown. MIS-structures on MMT as with anodic oxide and with oxinitrid silicon deposition after removal anodic oxide. A nature of defects of a transient layer between oxide and MMT is discussed which requires further research. Passivation MMT by deposition SixOyNz allows to reach rather low concentration surface charge, that on the order is lower, than with anodic oxide.

Threshold characteristics of p-Si-PtSi barriers with highly-doped surface nanolayer

Platinum silicide Schottky barrier detectors are widely used for application in the medium infrared wavelength region. The increase of cutoff wavelength and responsivity of PtSi-Si photodevices is possible by formation of highly-doped thin layer near to the semiconductor surface. We propose for this aim to form highly-doped nanolayer in p-Si by recoil implantation of boron. It is experimental established that profile of impirity distribution in surface layer is exponential. The doping concentration at the silicide/silicon interface is 1018 - 1020 cm-3 and thickness of surface layer is 8 - 12 nm. We have calculated the spectral, threshold, and noise characteristics of p-Si-PtSi photodetectors with highly-doped surface layers produced by molecular-beam epitaxy and short-pulse dopant implantation by a recoil method.

Conductivity anisotropy of CdHgTe MBE layers with a periodic surface microrelief

The surface microrelief of CdHgTe layers grown by molecular-beam epitaxy (MBE) method has been studied by means of atomic-force microscopy. A periodic surface microrelief in the form of an ordered system of extended waves with the characteristic period 0.1-0.2 μm has been detected on epilayers grown at increased temperatures. Angular dependencies of the conductivity at 77 K have been measured and the conductivity anisotropy has been detected with a minimum in the direction transverse to microrelief waves. A feature of the transmission system and the spectrum change after film annealing are observed. It is assumed that walls growing in the direction from the substrate to the surface are formed under microrelief waves slopes. Such structure can cause the observed feature of the transmission spectrum if the adjacent walls have different composition. In this work a calculation of spectral characteristics taking into account the influence of variable-gap composition and nonuniformity of the composition through the depth has been carried out.

Energy band diagrams of PtSi-Si barrier with a heavily doped surface nanolayer formed by recoil implantation

The development of Schottky barrier technology for creation of IR-photodetectors is caused by reduction of a potential barrier height used by formation of heavily-doped thin layer near to the semiconductor surface. We propose for this aim to form heavily-doped nanolayer in p-Si by recoil implantation of boron. Boron nm-thick film was deposited on the Si sample surfaces by cathode sputtering. After that the samples were irradiated by high intensity Al+ beams extracted from pregenerated explosion-emission plasma. The samples are examined by secondary ion mass-spectrometry (SIMS). It is experimental established that profile of impurity distribution in surface layer is exponential. The doping concentration at the silicide/silicon interface is 1018-1020 cm-3 and thickness of surface layer is 8 - 12 nm. The energy band diagrams of a PtSi - p- Si Schottky barrier with high-doped surface layer formed by recoil implantation were calculated for different parameters of barrier. It is shown, that effective barrier heights in PtSi-Si with recoil implantation formed surface 10 nm layer at surface concentration order 1020 cm-3 is reduced to 0.13 eV, corresponding to a cutoff wavelength of 9.5 micrometers . Thus, the cutoff wavelength of the PtSi Schottky infrared detectors has been extended to the long wavelength infrared region by incorporating a p+ doping layer with exponential profile of impurity distribution at the silicide/silicon interface.

Photosensitive structures using Hg1-xCdxTe solid solutions grown by molecular beam epitaxy

Parameters of Hg1-xCdxTe epitaxial structures produced by molecular beam epitaxy are presented. Results of measurements of the carrier recombination lifetime, sensitivity and the noise voltage of photosensitive elements have been studied. A high detectivity was obtained over a broad wavelength range.