Study of deep level defects in doped and semi-insulating n-6H-SiC epilayers grown by sublimation method

Deep level transient spectroscopy (DLTS) is employed to study deep level defects in n-6H-SiC (silicon carbide) epilayers grown by the sublimation method. To study the deep level defects in n-6H-SiC, we used as-grown, nitrogen doped and nitrogen-boron co-doped samples represented as ELS-1, ELS-11 and ELS-131 having net (N_D–N_A) ∼2.0×10¹² cm⁻³, 2×10¹⁶ cm⁻³ and 9×10¹⁵ cm³, respectively. The DLTS measurements performed on ELS-1 and ELS-11 samples revealed three electron trap defects (A, B and C) having activation energies E_c – 0.39 eV, E_c – 0.67 eV and E_c – 0.91 eV, respectively. While DLTS spectra due to sample ELS-131 displayed only A level. This observation indicates that levels B and C in ELS-131 are compensated by boron and/or nitrogen–boron complex. A comparison with the published data revealed A, B and C to be E₁/E₂, Z₁/Z₂ and R levels, respectively.     

Deep level transient spectroscopy in Hg1−xCdxTe

We report the application of Deep Level Transient Spectroscopy (DLTS) in Hg_1-xCd_xTe, demonstrating for the first time the utilization of DLTS techniques in a narrow band-gap semiconductor, E_g < 0.40 eV. DLTS measurements performed on an n⁺-p diode with E_g (x=0.21, T=30 K) =0.096 eV have identified an electron trap with an energy of E_v + 0.043 eV and a hole trap at E_v + 0.035 eV. Measurements of trap densities, capture cross sections, and the close proximity of the electron and hole trap locations within the band-gap suggest that DLTS may be observing both the electron and hole capture at a single Shockley-Read recombination center. The trapping parameters measured by DLTS predict minority carrier lifetime versus temperature data to be comparable with the experimentally measured values.     

Inductively coupled plasma induced deep levels in epitaxial n-GaAs

The electronic properties of defects introduced by low energy inductively coupled Ar plasma etching of n-type (Si doped) GaAs were investigated by deep level transient spectroscopy (DLTS) and Laplace DLTS. Several prominent electron traps (E_c—0.046 eV, E_c—0.186 eV, E_c—0.314 eV. E_c—0.528 eV and E_c—0.605 eV) were detected. The metastable defect E_c—0.046 eV having a trap signature similar to E1 is observed for the first time. E_c—0.314 eV and E_c—0.605 eV are metastable and appear to be similar to the M3 and M4 defects present in dc H-plasma exposed GaAs.     

An interpretation of dlts spectra of Al/Si3N4/ultrathin SI/GaAs structures — Effect of quantum well or interface states?

We discuss DLTS andC-V measurements on Al/Si₃N₄/Si(2nm)/n-GaAs (≈ 5×10¹⁷ cm^?3) structures. Three discrete deep traps superimposed on a U-shaped interface-state continuum have been identified, with respective thermal energies:E _c?0.53 eV,E _c?0.64 eV, andE _v+0.69 eV. The second one (0.64 eV) is presented as an electric field sensitive level, its enhanced phonon-assisted emission resulting in a rapid shift of the corresponding DLTS peak to lower temperatures, as the applied (negative) reverse bias voltage increases. An interpretation through emission from the quantum well, introduced by means of the intermediate ultrathin Si layer, has failed.     

On EAS spectrum with extremely low content of hadrons in the primary-energy range ∼10<Superscript>14</Superscript>−10<Superscript>15</Superscript> eV

The distribution of energy fluxes of the hadron component of extensive air showers through an ion-ization calorimeter in the primary-energy range ～3 × 10¹³?10¹⁶ eV is considered. Extensive air showers with zero and minimum energy fluxes of the hadron component are selected. It is concluded that the primary-energy range E ₀ ≈ 1 × 10¹⁴?2 × 10¹⁵ eV contains isotropic γ radiation with a spectrum close to bell-shaped, having a maximum near E ₀ ≈ 2.2 × 10¹⁴ eV and an additional peak near E ₀ ≈ 1.6 × 10¹⁵ eV.     

Sequence of different types of nonlinear current oscillation in n-GaAs

In_xGa_1– xAs(x}<0.03)/GaAs lasers grown by vapor phase epitaxy using an In/Ga alloy source were characterized by double crystal X-ray (DCX) diffraction and deep level transient spectroscopy (DLTS) measurements. Based on the results obtained from (400), (511), and (¯511) DCX rocking curves, the obvious effect of In incorporation is to give an increase in the full width at half maximum of the rocking curves that correlates with a coherency of the epitaxial layers. From DLTS spectra according to the In content, the most prominent electron deep traps areE 4 (E _c-0.58eV) andE5 (E _c-0.84eV). TheE 4 trap density increases with In content while the change ofE 5 trap density is not monotonic. The trend ofE 5 trap densities versus In content is very similar to that of etch pit densities (EPDs), that is, a minimum in EPD andE 5 trap density is observed at an In content ofx0.003 but beyond this value the densities increase again with In content.     

Electron irradiation of ion-implanted n-type Si-SiO2 structures studied by deep-level transient spectroscopy

2 structures implanted with 50-keV boron ions is studied by deep-level transient spectroscopy (DLTS) measurements. The DLTS spectra of ion-implanted samples exhibit one peak which corresponds to a deep level located in the forbidden gap of the silicon matrix at E_c-0.40 eV below the conducting band edge. New additional shallower levels are found in the spectra following bombardment by high-energy electrons, the peak intensity being dependent on the irradiation dose. The corresponding activation energy of the created defects, the density of the traps, and the electron-capture cross sections are evaluated. Received: 27 October 1997/Accepted: 8 December 1997     

Study of non-exponential electron capture by the main electron trap in GaAs0.62P0.38

In deep level transient spectroscopy (DLTS) exponentiality of level population changes in thermal emission as well as in capture processes is assumed. This is however, contrary to what is often observed in experiment. In this paper a model for interpretation of DLTS data in the case of non-exponential capture of electrons is proposed. It is assumed that the height of the capture of carrier changes locally according to the Gaussian distribution This model is applied to the case of deep electron trap with thermal activation energy equal to ΔE_B = 0.39 eV, observed in VPE GaAs_0.62P_0.38. Te. This model provides a capture barrier as well as a capture cross-section which are different from the ones predicted by the exponential transient model i.e., the ones derived from the slope of capacitance changes due to the filling pulse versus pulse duration at very short times.     

Fine and hyperfine structure of <Emphasis Type="Italic">P</Emphasis>-wave levels in muonic hydrogen

Corrections of order α ⁵ and α ⁶ are calculated for muonic hydrogen in the fine-structure interval ΔE ^fs = E(2P _3/2) − E(2P _1/2) and in the hyperfine structure of the 2P _1/2-and 2P _3/2-wave energy levels. The resulting values of ΔE ^fs = 8352.08 μeV, ΔẼ ^hfs(2P _1/2) = 7819.80 μeV, and ΔẼ ^hfs(2P _3/2) = 3248.03 μeV provide reliable guidelines in performing a comparison with relevant experimental data and in more precisely extracting the experimental value of the (2P–2S) Lamb shift in the muonic-hydrogen atom. Original Russian Text ? A.P. Martynenko, 2008, published in Yadernaya Fizika, 2008, Vol. 71, No. 1, pp. 126–136.     

New Constraints on the Axion–Photon Coupling Constant for Solar Axions

Resonance excitation of the ⁸³Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|g_Aγ × m_A| ≤ 6.3 × 10 ^-17 In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of m_A ≤ 12.7 eV at 95% C.L.     

Electronic and annealing properties of the E0.31 defect introduced during Ar plasma etching of germanium

Low energy (±80 eV) Ar plasma etching has been successfully used to etch several semiconductors, including GaAs, GaP, and InP. We have studied the only prominent defect, E_0.31, introduced in n-type Sb-doped Ge during this process by deep level transient spectroscopy (DLTS). The E_0.31 defect has an energy level at 0.31 eV below the conduction band and an apparent capture cross-section of 1.4×10⁻¹⁴ cm². The fact that no V-Sb defects and no interstitial-related defects were observed implies that the etch process did not introduce single vacancies or single interstitials. Instead it appears that higher order vacancy or interstitial clusters are introduced due to the large amount of energy deposited per unit length along the path of the Ar ions in the Ge. The E_0.31 defect may therefore be related to one of these defects. DLTS depth profiling revealed the E_0.31 concentration had a maximum (6×10¹³ cm⁻³) close to the Ge surface and then it decreased more or less exponentially into the Ge. Finally, annealing at 250 °C reduced the E_0.31 concentration to below the DLTS detection limit.     

Electronic structure and energies of interatomic bonds in the TiSi<Subscript>2</Subscript> compound with a <Emphasis Type="Italic">C</Emphasis>49 crystal structure

Full-electron calculations of the electronic structure of the TiSi₂ compound in the structural modification C49 are performed using the augmented-plane-wave method. The total energy, the electronic band structure, and the density of states are calculated for an extended translational unit cell Ti₄Si₈, which is formed during the growth of a silicon nanowire on a p-Si substrate. Calculations are also carried out for two orthorhombic unit cells of the nonstoichiometric compositions Ti₃Si₉ and Ti₅Si₇. The energies of the interatomic bonds are determined to be E _Si-Si = 1.8 eV, E _Ti-Ti = 2.29 eV, and E _Ti-Si = 4.47 eV. The dependence of the total energy of the unit cell E _tot(V) on the unit cell volume V is obtained by optimizing the unit cell volume. The bulk modulus B ₀ = 132 GPa is determined from the Murnaghan equation of state for solids and the dependence E _tot (V). This value of the bulk modulus is used to estimate the activation energy for interstitial diffusion of silicon atoms Q _i(Si) ≈ 0.8 eV.     

The defects produced by electron irradiation in tellurium-doped germanium

Abstract

The nature of the irradiation induced defects in germanium single crystal doped with tellurium was studied by DLTS and electrical measurements.

The E_c-0.21 eV level produced by irradiation with 1.5 MeV electrons was studied by DLTS technique. It was found that the defect associated with the E_c-0.21 eV level is divacancy. The E-center like defect (group V impurity-vacancy pair) introduces the E_c-0.20 eV level in samples doped with group V impurity. The level introduced by tellurium (group VI impurity)-vacancy pair is located at deeper than E_c-0.21 eV.

The E_c-0.16 eV level was generated by the annealing at 430 K. A model for the defect associated with the level is proposed to be a tellurium-vacancies complex.     

Post-collision interaction in inner-shell ionisation of ArL 3 by electron impact

The shifts and shapes of ArL ₃ Auger lines due to the post-collision interaction (PCI) in the inner-shell ionisation of theL ₃-shell of argon by electron impact have been measured for the range of excess energiesE ₁=10 to 1,500 eV. The experimental shifts {ie67-01} could be fitted by a relation {ie67-02} withc=(5.3±0.4) andn= (?0.45±0.04) whereГ(ArL ₃)=130 meV is the ArL ₃-level width. In a classical model the PCI shifts have been calculated for two limiting cases:a) whereE ₁ is large enough (E ₁>50 eV) for the motion of the two slow electrons to be treated as uncorrelated, andb) forE ₁→0. The calculated shifts forE ₁=250, 750 and 1,750 eV are in good agreement with the experimental results. Also the calculated PCI distorted shapes of Auger lines for differentE ₁ agree reasonably with the experimental Auger line shapes.     

Characterization of defects introduced in Sb doped Ge by 3 keV Ar sputtering using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS)

We have used deep level transient spectroscopy (DLTS), and Laplace-DLTS to investigate the defects created in antimony doped germanium (Ge) by sputtering with 3 keV Ar ions. Hole traps at E_V+0.09 eV and E_V+0.31 eV and an electron trap at E_C−0.38 eV (E-center) were observed soon after the sputtering process. Room temperature annealing of the irradiated samples over a period of a month revealed a hole trap at E_V+0.26 eV. Above room temperature annealing studies revealed new hole traps at E_V+0.27 eV, E_V+0.30 eV and E_V+0.40 eV.     

Evidence for a double charge transfer contribution to SERS in the Ag/Ag (CN)2− system

Using a square wave potential perturbation and monitoring the Raman intensity in parallel, the potential dependence of Ag(CN)₂⁻ spectra was studied with different exciting wavelengths. A double peak structure was found for the C-N stretch frequency both peaks having different excitation characteristics. In addition, the quenching rate of ad-complexes was measured at negative potentials together with the activation energy. From E_A = 75 kJ mol⁻, the energy of an acceptor level can be estimated located about 3 eV above E_F. This level presumably corresponds to the Ag 5s orbital which is shifted upwards due to the interaction with the ligands of the ad-complex. Since the CN⁻ 5σ or 1π orbitals form a donor level, the possibility of a double charge transfer contribution to the SERS enhancement exists.     

Interstitial iron and iron-acceptor pairs in silicon

Deep levels in iron-dopedp-type silicon are investigated by means of Deep Level Transient Spectroscopy (DLTS) and the Hall effect. Pairs of Fe with the acceptors B, Al, and Ga are observed at 0.1, 0.19, and 0.24 eV above the valence band edgeE _v. For interstitial iron, (Fe _i ), a level energy ofE _v+0.39+-0.02 eV is obtained with DLTS after correction with a measured temperature dependence of the capture cross section. The Hall effect yieldsE _v+0.37 eV for Fe_i. The annealing behavior of levels related to Fe is investigated up to 160 °C. Iron participates in at least four different types of impurity states: Fe _i , Fe-acceptor pairs, precipitations (formed above 120 °C) and an additional electrically inactive state, which is formed at room temperature.     

Influence of annealing on the conductivity and photoconductivity of p-type CdTe

On annealing p-type CdTe, considerable change in conductivity takes place. Samples of high resistivity were used for the measurements. Each of a set of samples was annealed at different temperature. After annealing, the temperature dependence of the conductivity and the relaxation curves of the photoconductivity were measured. Analysis of the first set of curves yielded value of energyE _a corresponding to the level occurring in given samples. It was established that this acceptor level is due to V^cd, or V^cd complexes, and is situated at 0.3 eV above the valence band edge. Concentration of these levels is increased by annealing. Furthermore, an energy value ofH=0.79 eV was found, corresponding very probably to the formation energy of a vacancy V^cd.Analysis of the relaxation curves yielded the temperature dependence of _S , _T and the energy distanceE _M of the impurity level that is responsible for photoconductivity. A value of (E _g -E _M )=0.09–0.12 eV was found for all samples studied. This level therefore lies below the conduction band edge and its concentration amounts to 10¹⁴–10¹⁵ cm^–3. The level is probably due to foreign impurities.Two sets of samples were used: both as-grown and Sb-doped. The results for both sets were not much different from each other.Ke Karlovu 3, Praha 2, Czechoslovakia.     

Chromium and chromium-boron pairs in silicon

Four different measurement techniques: EPR, NAA, DLTS, and luminescence were applied to characterize the properties of chromium in silicon. The solubility of chromium in silicon was determined and its pairing reaction with boron was studied. The energy level atE _c?0.23 eV was attributed to interstitial chromium and a second level atE _v+0.27 eV was correlated to chromium-boron pairs. The luminescence band of the chromium-boron pairs was clearly identified. The properties of chromium are compared with those of other transition metal impurities in silicon crystals.     

注硅半绝缘GaAs的深能级

用深能级瞬态谱(DLTS)详细研究了硅离子注入Liquid-encapsulated Czochralski(缩写为LEC)半绝缘GaAs的深中心。结果表明,在注硅并经高温退火的有源区中观测到4个多子(电子)陷阱,E₀₁,E₀₂,E₀₃和E₀₄。它们的电子表观激活能分别为0.298,0.341,0.555和0.821eV。其中E₀₄与EL2有关,但不是EL2缺陷。E₀₄的电子 关键词：