高纯度砷化镓外延薄膜剩余受主杂质的研究

本文用光致发光法(4.2°K和1.8°K)研究高纯度LPE-GaAs和VPE-GaAs的剩余受主杂质。实验结果表明,高纯LPE-CaAs的剩余受主杂质为C、Si、Ge,而在AsCl3-Ga-H2系统中生长的高纯VPE-GaAs的剩余受主杂质为C、Zn、Si、Ge。但是在AsCl3-Ga-N2系统中生长的高纯VPE-GaAs只检测到受主杂质碳。本文还研究某些生长条件对杂质引入的影响。     

Intensities of the line and photoionization spectra of shallow nonhydrogenlike impurities in semiconductors

Numerical nonvariational methods are proposed for the calculation of energies and wave functions of bound states, ground state wave functions with the account of central cell corrections, and the orthonormalized wave functions of the continuous spectrum of nonhydrogenlike shallow impurities in semiconductors. A number of different spectral characteristics is calculated for donor impurities in Ge and Si and for acceptor impurities in Ge and GaAs. The theory of photofield ionization i.e. tunnel ionization of an optically excited impurity atom is presented for shallow donors with the account of the effective mass anisotropy. The possibility of the observation of the line spectrum (due to transitions to shallow Coulomb excited levels) of a deep impurity in the presence of a high magnetic field is shown.     

Electrophysical properties of gallium arsenide in combination with impurity-doped germanium and isovalent indium and antimony impurities

The temperature dependence of the charge carrier concentration and mobility in n-type GaAs monocrystals doped jointly by Ge and isovalent In and Sb impurities is investigated. The observable charge carrier concentration and mobility changes in the GaAs:Ge:In and GaAs:Ge:Sb are compared with the corresponding characteristics in GaAs:Ge, and the change in properties along the ingots can be explained by the Ge impurity redistribution in the gallium and arsenic sublattices in the presence of an isovalent impurity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 3–8, September, 1987.     

Force-constant changes due to impurities in Si and Ge

Force-constant softening due to impurities in Si and Ge has been estimated, using the band model of sievers and Takeno, to be between 10–15%. The molecular model yields a value of about 20% for the same effect.     

The dependence of the phonon-resistivity on the residual resistivity in the Al-Ge and Al-Ga alloys

The electrical resistivity of aluminum based alloys containing s-p (Ge, Ga) impurities has been measured at 15, 20, 35 and 50 K. It was found that the temperature-dependent part of the resistivity ?(T) - ?₀ has a logarithmic dependence on ?₀ and is independent of the kind of impurities.     

Band gap narrowing and doping level of heavily doped Germanium nanocrystals deduced from photoconductivity studies

We investigate the photoconductivity of a n⁺-ZnO/n-Ge NCs/p⁺-GaAs junction where the active layer consists of heavily n-doped Ge NCs synthesized in the gas phase. Measurement of a significant current at energies smaller than the band gap of GaAs demonstrates the photogeneration of charge carriers by the Ge NCs. From the correlation of the NC size with the absorption threshold, a narrowing of the direct band gap in the Ge NC thin film is obtained and attributed to the heavy doping of the Ge NCs. A remarkably high electrical activation of ~15% is found for the incorporated P impurities in the NCs.     

Localized electric-field-enhanced low-light detection by a 2D SnS visible-light photodetector

Due to their excellent carrier mobility, high absorption coefficient and narrow bandgap, most 2 D IVA metal chalcogenide semiconductors(GIVMCs, metal = Ge, Sn, Pb;chalcogen = S, Se) are regarded as promising candidates for realizing high-performance photodetectors. We synthesized high-quality two-dimensional(2 D) tin sulfide(Sn S) nanosheets using the physical vapor deposition(PVD) method and fabricated a 2 D Sn S visible-light photodetector. The photodetector exhibits a high photoresponsivity of 161 A·W~(-1) and possesses an external quantum efficiency of 4.45 × 10~4%, as well as a detectivity of 1.15 × 10~9 Jones under 450 nm blue light illumination. Moreover, under poor illumination at optical densities down to 2 m W·cm~(-2), the responsivity of the device is higher than that at stronger optical densities. We suggest that a photogating effect in the 2 D Sn S photodetector is mainly responsible for its low-light responsivity. Defects and impurities in 2 D Sn S can trap carriers and form localized electric fields, which can delay the recombination process of electron-hole pairs,prolong carrier lifetimes, and thus improve the low-light responsivity. This work provides design strategies for detecting low levels of light using photodetectors made of 2 D materials.     

Theory of shallow donor impurity near-surface states in Si and Ge

Previously developed methods for determining the wave functions and energy levels of shallow donor impurities on the surface or in the bulk of a semiconductor have been extended to the case of impurities at a finite depth from the surface. Calculations were performed for impurities near either a (100) or (111) surface in Sci and for a (111) surface in Ge. The ground state and the excited state having the largest electric dipole coupling to the ground state wete determined. In addition, the optical absorption cross section for transitions from the ground state to this excited state were calculated for surface and near surface states. These results were used to calculate a theoretical absorption spectrum for Si doped uniformly to a depth of 10 atomic layers.     

Dopant-assisted concentration enhancement of substitutional Mn in Si and Ge

The influence of p- and n-type electronic dopants on Mn incorporation in bulk Si and Ge is studied using first-principles calculations within density functional theory. In Si, it is found that the site preference of a single Mn atom is reversed from interstitial to substitutional in the presence of a neighboring n-type dopant. In Ge, a Mn atom is more readily incorporated into the lattice when an n-type dopant is present in its immediate neighborhood, forming a stable Mn-dopant pair with both impurities at substitutional sites. A detailed analysis of the magnetic exchange interactions between such pairs reveals a new type of magnetic anisotropy in both systems.     

A lattice model of thermopower in hopping conduction: Application to neutron-doped crystalline germanium

A model for describing hopping thermopower is proposed. Within the model, the majority and compensating impurities form a simple cubic lattice in a crystal matrix. The thermopower associated with hole (electron) hopping over hydrogen-like impurities is calculated with inclusion of their excited states. The results of calculations are compared with available experimental data on the low-temperature thermopower of Ge: Ga and the specific heat of Si: P in the dielectric region of the insulator-metal transition.     

Effect of As doping on the photoluminescence of nanocrystalline Ge embedded in SiO2 matrix

Samples of nanocrystalline ⁷⁴Ge embedded in amorphous SiO₂ film were prepared by ⁷⁴Ge ion implantation and subsequent primary thermal annealing. These samples were irradiated by neutron flux in a nuclear reactor then the second annealing followed. Irradiation with thermal neutrons leads to doping of nanocrystalline ⁷⁴Ge with As impurities due to nuclear transmutation of isotope ⁷⁴Ge into ⁷⁵As. Transmission electron microscope, X-ray fluorescence, X-ray photoelectron spectroscopy, laser Raman scattering and photoluminescence of the obtained samples were measured. It was observed that with the increase in As-donors concentration, photoluminescence intensity first increased but then significantly decreased. An explanatory model of this non-monotonic behavior was discussed.     

Impurity-Vacancy Complexes in Si and Ge

We examine the electronic and geometrical structure of impurity-vacancy complexes for 11 sp-impurities in Si and Ge, using the pseudopotential plane wave (PPW) and the all-electron Kohn–Korringa–Rostoker (KKR) methods. We find that all impurities of the 5sp and 6sp series prefer the split-vacancy configuration. For Cd and Sn we obtain good agreement of the calculated hyperfine parameters with experimental PAC and EPR data. Impurities of the 3sp and 4sp series form distorted substitutional complexes (except Al, which forms a split complex in Si). This trend strongly correlates with the lattice relaxations of nearest neighbors around the isolated (without vacancy) substitutional impurities.     

Regular periodic “explosions” of electron—hole drops under steady-state illumination and microwave heating

DC conductivity measurements on (strained) Ge at 4 K under steady-state illumination show that even in the presence of fairly strong steady-state microwave heating electron—hole drops continue to form, but rather than assuming a steady-state they “explode” periodically. The results are readily explained by — and provide corroboration for — a model by Altukhov.     

超导Nb-Ge溅射膜的俄歇电子能谱及电子能谱化学分析

利用表面分析仪器俄歇电子能谱(AES)仪和电子能谱化学分析(ESCA)仪对超导Nb-Ge溅射膜进行表面和深度剖面分析,以探讨在溅射沉积成膜过程中A15结构Nb₃Ge能够稳定生长的机制,以及影响其转变温度T_c的因素。分析结果表明,超导Nb-Ge膜中含有O,C和Al等杂质,其中O的含量对T_c有重要影响。表面上未发现有聚集的Ge。Nb/Ge密度比由表面层的3.1向内部逐渐降至2.26。X射线光电子能谱(XPS)的分析表明:Nb,Ge,C和O的谱峰沿深度均有不同程度的化学位移和峰形变化,这明这些元素的化学态在膜内是复杂的。但其中Nb的变化最小,可能对高T_cA15Nb₃Ge相的生长起稳定作用。 关键词：     

Correlation between the anisotropy of hopconduction magnetoresistance and reciprocal band masses in Ge

Near 70 kG the d.c. magnetoresistance of phonon-assisted hopping of charge carriers between shallow impurities is found to have an anistropy depending on the reciprocal effective mass calculated from the L₁ conduction band minima in the case of n-type Ge and from the heavy hole component of the Γ′₂₅ valence band maximum in case of p-type Ge. These correlations are discussed and it is suggested that they are connected with the symmetry of the impurity wave functions and that the magnetic field tends to remove the light hole component of an acceptor wave function.     

EPR and ENDOR investigations of Ge,Sn and Pb impurities in CdSe

Electron paramagnetic resonance (EPR) experiments of light activated Ge, Sn and Pb impurities in wurtzite type CdSe crystals are presented. These²S_1/2 centres exhibit a large hyperfine structure which shows a variation with temperature. 25 shells of neighbour nuclei are resolved for CdSeSn by means of the Electron nuclear double resonance (ENDOR) technique. All shells belong to one of three distinct shell symmetries of the lattice thus confirming a high symmetry defect. Additional Sn respectively Ge related spectra are described and interpreted as complex centres correlated with lithium.     

Crystal structures,phase relationships,and magnetic phase transitions of R_5M_4 compounds (R = rare earths,M = Si,Ge)

Our recent studies of the crystal structures, phase transitions, and magnetic properties of intermetallic compounds R5M4 (R = rare earths; M = Si, Ge) are reviewed briefly. First, crystal structures, phase relationships, and magnetic properties of several 5:4 compounds, including Nd5Si4xGex , Pr5Si4xGex, Gd5xLaxGe4,La5Si4, and Gd5Sn4 , are presented. In particular, the canted spin structures as well as the magnetic phase transitions in Pr5Si2Ge2 and Pr 5 Ge 4 investigated by neutron powder diffractions and small-angle neutron scattering are reviewed. Second, the crystal structures and magnetic properties of the most studied compounds Gd5(Si,Ge)4 are summarized. The focus is on the parent compound Gd5Ge4 , which is an amazing material exhibiting magnetic anisotropy, angular dependent spin-flop transition, metastable magnetic response, Griffiths-like phase, thermal effect under pulsed fields, antiferromagnetic and ferromagnetic resonances, pronounced effects of impurities, and high-field induced magnetic transitions.     

Ferromagnetism in epitaxial germanium and silicon layers supersaturated with managanese and iron impurities

The possibility of laser synthesis of diluted magnetic semiconductors based on germanium and silicon doped with manganese or iron up to 10–15 at % has been shown. According to data on the electronic levels of 3d atoms in semiconductors, Mn and Fe impurities are most preferable for realizing ferromagnetism in Ge and Si through the Ruderman-Kittel-Kasuya-Yosida mechanism. Epitaxial Ge and Si layers 50–110 nm in thickness were grown on gallium arsenide or sapphire single crystal substrates heated to 200–480°C. The content of a 3d impurity has been measured by x-ray spectroscopy. The ferromagnetism of layers and high magnetic and acceptor activities of Mn in Ge, as well as of Mn and Fe in Si, are manifested in the observation of the Kerr effect, anomalous Hall effect, high hole conductivity, and anisotropic ferromagnetic resonance at 77–500 K. According to the ferromagnetic resonance data, the Curie point of Ge:Mn and Si:Mn on a GaAs substrate and of Si:Fe on an Al₂O₃ substrate is no lower than 420, 500, and 77 K, respectively.     

Mu centers in crystalline Ge under illumination

A slow conversion to a diamagnetic state has been observed for muonium centers at the tetrahedral interstitial site (Mu⁰ _T) in dark Ge at low temperatures. While the conversion process is affected by illumination, no effect of illumination upon the initial (Mu⁰ _T) centers themselves was observed at 10 K. This is in marked contrast with the case of (Mu⁰ _T) centers in Si where strong interaction with photo‐induced carriers is observed, suggesting that the electronic level associated with (Mu⁰ _T) state in Ge is not located in the energy gap. This revised version was published online in August 2006 with corrections to the Cover Date.     

Freely adjusted properties in Ge–S based chalcogenide glasses with iodine incorporation

In this study, we examined the function of halogen iodine acting as a glass network modifier in green chalcogenide glasses based on the Ge–S system. We obtained a series of Ge–S–I glasses and determined their glass-forming region. We then recorded the physical, thermal, and optical properties and studied the effect of halogen iodine on Ge–S–I glasses. Results show that these glasses have relatively wide optical transmission window for infrared (IR) applications. The softening temperature of Ge–S–I glasses varies from 210.54 °C to 321.63 °C, this temperature fits well with some kinds of high-temperature polymers, such as PES and PEI, the polymers serve as protective layers with high strength and flexibility, thus simplifying the fabrication processes of IR chalcogenide glass fiber. Finally, we performed a purification process to eliminate impurities and to improve optical spectra.