Silicon Trap Research Articles

Stability under vacuum of silicon trap detectors and their use as transfer instruments in cryogenic radiometry

The stability of the responsivity of trap detectors under vacuum has been studied by means of a special chamber designed for the test of photodetectors at low pressure. The first experiments at a wavelength of 647 nm show that the responsivity variations are smaller than the uncertainties of the measurements, approximately 3 parts in 10(5), when the detector operates successively in air, under vacuum, and then again in air. Calculations based on experiments with single windowless photodiodes indicate that the change in trap responsivity that is due to vacuum effects should be smaller than 1 part in 10(5), at least in the visible part of the wavelength range. This stability makes trap detectors suitable for cryogenic radiometry when one uses transfer detectors under vacuum.

Polarization dependence of trap detectors

The sensitivity of a series of silicon trap detectors has been measured as a function of beam polarization. Measurements and numerical simulation show that very small departures from the ideal orientation of the photodiodes mounted in the trap induces a significant sensitivity to the state of polarization of the beam. Consequences of this polarization dependence for the use of trap detectors as transfer detectors in high-accuracy applications, particularly in cryogenic radiometry, are discussed.

Comparison of luminous-intensity scales based on trap detectors and incandescent lamps

New luminous-intensity scales have been developed in Finland and Sweden based on silicon trap detectors having responsivities compared with an absolute cryogenic radiometer at a wavelength of 543,516 nm. The low reflectance of the trap device makes it possible to use a V(λ) filter in conjunction with the trap where the filter is separately characterized in transmittance. The new scales were compared with the scale currently in use in Sweden, which is based on incandescent lamps calibrated by the Bureau International des Poids et Mesures (BIPM). The agreement of the scales is generally within ±1%. The Finnish scale was typically 0,2% to 0,6% below the BIPM-based scale, and the trap-based scale of Sweden is typically 0% to 0,5% below the BIPM-based scale when compared at a measurement distance of 4 m. Different sizes of aperture and different distances to the source showed variations up to ±1%. The transmittances of the V(λ) filters were measured separately by the two institutes and showed an agreement better than 0,1% in the colour-correction factor.

Effect of implanted fluorine on MOS structures with sputtered SiO2 insulator

Fluorine was introduced by ion implantation into MOS structures with sputtered oxide. After annealing, its effects on the high-frequency C-V curve and Fowler-Nordheim tunnelling barrier height were studied. An increase of acceptor dopant concentration in the substrate was observed due to the fluorine implantation. The presence of fluorine increased the Fowler-Nordheim tunnelling barrier height for electron injection from both metal and silicon. The role of fluorine is explained by a physical model similar to that used by Ma, where fluorine is assumed to bond with trivalent silicon trap centres in the sputtered oxide.

An easy and accurate method to determine simultaneously the free energy level and the capture cross section of a trap centre

A method which permits simultaneous determination of the values of the free energy of ionization, the capture cross section and the concentration of a trap in a semiconductor is presented. The method depends on an accurate fit of a set of analytical expressions to the experimental data obtained by studying the variation of transient capacitance amplitudes with the duration of a filling pulse bias in a junction experiment. The analytical expressions used are based on the rigorous theoretical model of Pons. Various criteria which must be observed to ensure reliable results are carefully worked out in detail. The effectiveness of the present method is demonstrated on two copper-induced electron traps in gallium arsenide phosphide and a laser radiation-induced electron trap in silicon.

Indium-vacancy interaction in laser-annealed silicon

The In-V complex in laser-annealed and proton-bombarded p-type and n-type silicon, doped with radioactive 111In atoms, was identified by means of perturbed angular correlation measurements. The complex dissociates at 130°C, corresponding with a dissociation energy of 1.0 eV. During the nuclear decay of 111In, the complex transforms into Cd-V which manifests itself in three different electronic configurations. Transitions between these configurations were observed to depend on temperature and doping of the sample. It is concluded that P as well as B atoms in silicon trap vacancies at room temperature. It is further concluded that the vacancy concentration in laser-annealed silicon amounts to at least 10 16–10 17 cm -3, which is an order of magnitude larger than what has been assumed so far.

Indium-vacancy interaction in laser-annealed silicon

Abstract The In-V complex in laser-annealed and proton-bombarded p-type and n-type silicon, doped with radioactive 111 In atoms, was identified by means of perturbed angular correlation measurements. The complex dissociates at 130°C, corresponding with a dissociation energy of 1.0 eV. During the nuclear decay of 111 In, the complex transforms into Cd-V which manifests itself in three different electronic configurations. Transitions between these configurations were observed to depend on temperature and doping of the sample. It is concluded that P as well as B atoms in silicon trap vacancies at room temperature. It is further concluded that the vacancy concentration in laser-annealed silicon amounts to at least 10 16 –10 17 cm -3 , which is an order of magnitude larger than what has been assumed so far.

Deep Levels Associated with Oxygen Precipitation in CZ Silicon and Correlation with Minority Carrier Lifetimes

AbstractA dominant electron trap in boron-doped CZ silicon at Ec −0.41 ± 0.02 eV with a electron capture cross section >10−14 cm2 has been observed with DLTS in 2-step annealed (16 hrs at 800°C + 16 hrs at 1050°C) seed end wafers where oxygen precipitation is pronounced. A strong correlation between the generation lifetime τg (as calculated from junction reverse generation currents) and the density of this trap is also observed. Electron microscopy showed the dominant precipitates to be {100} plate type containing only Si and 0, with dislocations and punched-out loops in close proximity. Wafers from the center- or tang-sections of the ingot or those given a 1-step anneal (conditions which result in much less oxygen precipitation) contain a low density (<1.2 × 1012 cm−3) of a hole trap at Ev +0.25 eV not correlated with Tg. These wafers contain precipitates with a different morphology with much rower or minimal dislocation densities. Possible origins of the lifetime controlling electron trap is discussed.

Photoluminescence of excitons bound to an isoelectronic trap in silicon associated with boron and iron

We describe the luminescent properties of an isoelectronic trap in silicon which needs boron and iron for its formation. The radiative recombination is due to an exciton localized at the trap. It exhibits no-phonon lines at 1.06640 and 1.066 76 eV corresponding to dipole-forbidden and dipoleallowed transitions from $J=2$ or $J=1$ exciton states split by 0.36 meV due to the electrostatic electron-hole interaction. The exciton couples strongly to a quasilocalized mode of 9.7-meV quantum energy, resulting in one- and two-phonon Stokes replicas of the no-phonon luminescence spectrum. The rather large oscillator strength of the "forbidden" transition in the local-mode spectrum indicates that the optical center is a hole trap. We discuss the formation and dissociation of the trap and show that essential luminescence data are inconsistent with an identification of the optical center with ${\mathrm{Fe}}_{i}{\mathrm{B}}_{s}$ pairs.

Localized exciton bound to an isoelectronic trap in silicon

A photo- and electroluminescence study is reported on the recombination radiation from excitons bound to an isoelectronic trap in silicon. This type of luminescence is novel in silicon. The luminescence which was obtained from only few samples consists of three long-lived emission lines $A$, $B$, and $C$, and a number of associated weak phonon wings. The decay characteristics and the temperature dependence of the fluorescence along with the forbidden $B$ line exhibited under perturbations of a magnetic or elastic strain field give rise to our interpretation in terms of an isoelectronic trap binding the electron-hole pair. These features are highly reminiscent of familiar isoelectronic systems which can bind an exciton such as GaP:N, GaP:Bi, or ZnTe:O. Orientational Zeeman measurements show that the trap has axial symmetry in the 111g direction. The $g$ factors are ${g}_{e}=1.6\ifmmode\pm\else\textpm\fi{}0.1$ and ${g}_{h}=1.1\ifmmode\pm\else\textpm\fi{}0.1$. The ${g}_{e}$ value is largely reduced in comparison with known bound-electron values and suggests that an electron is tightly bound to the trap capturing the hole by its Coulomb field. This conception also explains the observed cw-excitation dependence of the fluorescence. The samples showing the $A$, $B$, and $C$ fluorescence are $n$ and $p$ type ($\ensuremath{\rho}\ensuremath{\ge}2$ \ensuremath{\Omega} cm) and are grown by different techniques. The strongest fluorescence is observed from an aluminumdoped sample (2.5 \ensuremath{\Omega} cm) for which the trap density is estimated to be no more than some ${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. No correlation of luminescence with shallow-donor or -acceptor doping could be established, and the nature of the trap remains unidentified. A correlation of luminescence with carbon concentration in a number of samples and the annealing behavior of the exciton luminescence may hint that carbon is one of the trap constituents.

Excitons bound to an isoelectronic trap in silicon

Three novel emission lines in silicon. A, B, and C, are reported which are associated with an exciton bound to an isoelectronic trap. We deduce this interpretation from temperature dependent measurements as well as from Zeeman-, piezo-, and time-resolved spectroscopy. The binding center is assumed to involve carbon.

Tin as a Vacancy Trap in Silicon at Room Temperature

Silicon samples which contain a high concentration of dispersed tin have been irradiated at 80°, 140° or 300°K with 3 MeV electrons. The interaction of defects (vacancies and interstitials) with tin was studied by infrared absorption measurements. The tin-vacancy pair was found by monitoring the release of vacancies when the pair anneals near 460°K. Vacancies released from tin are then trapped on oxygen to form the oxygen-vacancy defect which is measured by the strength of the 835 cm-1 line. Because vacancies are trapped at room temperature by tin atoms, tin aids in the separation of vacancy and interstitial associated defects in silicon. An absorption band at 935 cm-1 produced independent of the tin concentration is attributed to silicon interstitials trapped by oxygen in Si. This interstitial defect is stable to 330°K. Applications to devices are suggested.

Reaction du plutonium avec les elements d'addition des colonnes III et IV B du tableau periodique, dans le magnesium allie

The influence of certain addition elements X on the diffusion of plutonium in Mg-X alloys has been studied. This study was done on diffusion couples consisting of Mg-Pu/Mg-X, where X is one of the elements of groups III B or IV B of the periodic table. Aluminium, gallium, silicon, germanium, tin and lead trap the plutonium in the form of intermetallic compounds PuAl 2, PuGa 2, PuSi 2 (Pu, Ge) Mg 2, PuSn 3, PuPb 3. These compounds were identified by microanalysis and X-rays.