P-doped Silicon Research Articles

Divacancies production in irradiated n-type silicon

Measurements of loss factor and capacitance made on single crystals of P-doped n-type silicon are reported. Samples are irradiated with (1.00 ± 0.20) MeV electrons at temperatures <12K. The production of divacancies in the irradiated samples is monitored using hopping conductivity changes at 4.2 K. Higher divacancy production is observed in Czochralski-grown samples and samples containing appreciable concentrations of group III impurities. This suggests that oxygen and group III impurities trap the self interstitials, mobile under irradiation conditions, thus, inhibiting divacancy-self-interstitials annihilation. Effects of irradiation on the free carriers conductivity of the samples are also investigated.

Fast P-doped silicon bolometer for detecting heat pulses

A new detector of ballistic phonons is presented. It is a P-doped Si bolometer realized on top of a (100)Si crystal by ion implantation. The open circuit responsivity of the bolometer is 8000 V/W and the response time less than 50 ns. Time-resolved spectra of ballistic phonons propagating in the same Si crystal along the 〈100〉 direction are reported.

Low-temperature radiation damage in silicon: I. Annealing studies on n-type material

The presence of electrically active defects in electron irradiated P-doped n-type silicon was monitored using capacitance and loss factor measurements. Irradiations were performed at temperatures ⪅12 K with electrons of energies ⪅1.50MeV. Seemingly, the concentration of single vacancies on the irradiated samples is low. This is deduced from the small recovery in the samples properties observed upon annealing at ∼75 K. Also two annealing stages observed at ∼140–150 K and ∼240 K are attributed to the self-interstitial. Electron traps observed at ∼( E c − 0.14) eV and ( E − 0.24) eV in the ga p are ascribed to the carbon interstitial and to the divacancy, respectively.

Temperature dependence of specific contact resistivity

The temperature dependence of specific contact resistivity has been measured over the range 77-380 K for W contact to both B- and P-doped silicon. A range of surface concentrations have been investigated. In general, ρ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> is slightly more weakly temperature dependent than has been predicted. There appears to be no fundamental barrier to obtaining low-resistance contacts for low-temperature (<100 K) device operation. Contact resistivity to very heavily P-doped surfaces actually decreases with decreasing temperature, in agreement with predictions.

Effect of organic contaminants on the oxidation kinetics of silicon at room temperature

The oxidation kinetics of HF-etched n- and p-doped silicon in air at room temperature have been studied by electron spectroscopy for chemical analysis. No great differences have been found between the n- and p-type oxidation kinetics at the low doping level of the studied samples. The rate of oxide growth on the HF-etched surface is much lower than that on a silicon surface obtained by fracture in air of a silicon monocrystal. The behavior of a silicon sample fractured in de-ionized water and then oxidized in air at room temperature is intermediate. The above findings have been interpreted on the basis of surface reactions involving the plasticizers of the HF and water containers. These reactions produce carbon-rich hydrophobic surfaces which retard the silicon oxide growth. A mechanism for the involved surface reactions is proposed.

Donor clusters in silicon. II. ESR simulations.

Previously reported ESR studies of P-doped silicon have been analyzed in terms of donor clusters. Simulated spectra based on a Poisson distribution of clusters and a binomial distribution of hyperfine intensity inadequately described the peak heights of the experimental data. In the present report, an alternative approach is taken which simulates the effects due to topological hyperfine and cluster-cluster interactions. A computer-generated system of donors is partitioned into clusters, retaining all interdonor exchange energies greater than some critical ${J}_{c}$. The matrix eigenvalue problem for each cluster is solved numerically and the results used to calculate transition energies and probabilities. Simulated spectra produced in this manner show good quantitative agreement with the data.

Inversion layer solar cells on chemically vapor-deposited polycrystalline silicon thin films

It is demonstrated that the metal-insulator-semiconductor (MIS) inversion layer (IL) process is also suited to fabricating solar cells on fine-grained polycrystalline silicon thin films prepared by low-pressure chemical-vapor deposition (LPCVD). Plasma enhanced silicon nitride was used as dielectric to create a highly conductive inversion layer at the silicon surface. As revealed by high frequency and quasistatic C-V measurements, the insulator/semiconductor interface for fine-grained LPCVD polycrystalline silicon is similar to that for the coarse-grained Wacker Silso material. An excellent external quantum efficiency in the short wavelength region was obtained for solar cells on both materials. For the 1-cm2 solar cell on 2-Ω cm p-doped LPCVD silicon an active area efficiency of ηa=1.8% was obtained. Ways of improving these cells are suggested. A total area AM1 efficiency of 13% was achieved for coprocessed 4-cm2 MIS-IL solar cells on Wacker Silso.

Phosphorus redistribution in P-doped polycrystalline silicon/tantalum silicide system during high temperature sintering

We studied redistribution of phosphorus between layers of P-doped polycrystalline silicon and TaSi2 during sintering of the silicide at 900 °C. Because of the loss of phosphorus to the silicide, the sheet resistivity of polysilicon layers is increased. We attempted a systematic study of this effect using polysilicon layers of varying thicknesses (from less than 1000 to more than 6000 Å). The experimental results are in excellent agreement with our model which regards the concentrations of phosphorus in both polysilicon and silicide as dilute solutions and assumes that during sintering of the silicide these solutions come to equilibrium. From the equilibrium condition of uniform chemical potential with respect to the solute, we were able to determine the distribution coefficient of P between the two solvents.

Modeling of carrier mobility against carrier concentration in arsenic-, phosphorus-, and boron-doped silicon

New carrier mobility data for both arsenic- and boron-doped silicon are presented in the high doping range. The data definitely show that the electron mobility in As-doped silicon is significantly lower than in P-doped silicon for carrier concentrations higher than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . By integrating these data with those previously published, empirical relationships able to model the carrier mobility against carrier concentration in the whole experimental range examined to date (about eight decades in concentration) for As-, P-, and B-doped silicon are derived. Different parameters in the expression for the n-type dopants provide differentiation between the electron mobility in As-and in P-doped silicon. Finally, it is shown that these new expressions, once implemented in the SUPREM II process simulator, lead to reduced errors in the simulation of the sheet resistance values.

Electron and ion beam effects in auger electron spectrometry

Abstract In Auger Electron Spectrometry relatively high primary electron current density is usually used in order to obtain a good signal-to-noise ratio. As a consequence, a number of phenomena occurs, which can substantially modify—or even destroy—the sample, and impair the results of the analysis. In this communication we report some observations on the electron and ion beam interaction on some of the insulating and conducting films used in the silicon device technology. Among the materials considered, silicon nitride and P-doped silicon dioxide are of primary interest, and will be treated in some detail; results on other films, both insulating (Al2O3, B-doped SiO2, etc.) and conducting (Al-Si alloys) will also be reported. The electron beam causes the oxides (B, Al, Si, P) to be reduced, as shown by the decrease of the height of the low energy, chemically shifted peaks (BKVV, AlLVV, SiLvv, PLvv) and by the contemporary increase of the height of the elemental peaks. In phosphorus doped glasses the electron beam also induces a strong surface P enrichment, followed by a P desorption. Silicon nitride was found to be quite stable against the e-b irradiation in “good” vacuum, but very sensitive to the e-b induced oxidation even at (total) pressure as low as 5 × 1010 torr. This is a very important fact to be taken into account when evaluating thin Si3N4 films, because it can change the apparent film stoichiometry. Some metallic films are also preferentially oxidized by the electron beam; in Al/Si diluted alloy (0.1÷2% silicon) a strong surface silicon enrichment was found to take phase on small-grained thin films, but not on bulk material. Our results show that much care has to be taken when performing or interpreting the AES data, and how to use, in some cases, the e-b irradiation effects to increase the sensitivity of the method.

Optical Properties of Heavily Doped Silicon between 1.5 and 4.1 eV

The optical constants of heavily doped silicon are determined between 1.5 and 4.1 eV with use of polarization modulation ellipsometry. For photon energies less than 3.4 eV it is found that there is a substantial increase in the optical absorption coefficient for As-doped silicon, but a much smaller increase for B-doped or P-doped silicon. It is believed that this is due to $d$-electron admixture into the conduction band when the dopant is As.

Positron annihilation in n- and p-type, B- and P-doped silicon crystals of 100 and 111 orientations

Positron annihilation spectra are compared for oriented and doped silicon crystals. A critical three-component deconvolution analysis of the lifetime spectra resulted in a previously undetected lifetime of ∼60 psec and ∼25% relative intensity. The sensitivity of the lifetimes to the details of analysis is discussed.

THE METAL-NON METAL TRANSITION IN DOPED SEMICONDUCTORS

Data of electric transport, magnetic susceptibility, and NMR in P-doped silicon are examined to give a picture of metal-non metal transition in doped semiconductor : the metallic transition is percolation of donor clusters which have undergone local Mott transition. Experiments below 1K suggest a possibility for electrons in metallic samples to condense into new phases at very low temperatures.

A parametric study of the surface potential and band bending in silicon

A unified approach to band bending is described, and the macroscopic electronic potential through the silicon surface is calculated as a function of temperature in the ranges 300–500°K and 100–1600°K, externally applied electric field, for zero field and for 10 3 to 10 5 V/cm, and donor and acceptor concentrations, from 10 12 to 10 18 cm −3. The results, presented in graphical and tabular forms, are intended to serve the convenience of researchers in a wide area of surface and high temperature silicon physics such as in thermionic, field, and photoelectric emission work and in high temperature, and field modulated transport studies. The calculations are based on an essentially classical approach to the solution of the electrostatic band bending problem, using the surface state density for silicon proposed by Allen and Gobeli on the basis of their photoelectric investigations. The cases considered were limited to nondegenerate, intrinsic, and n- and p-doped silicon in which all impurity states are fully ionized.

Shielded silicon gate complementary MOS integrated circuit

An electrostatic shield for complementary MOS integrated circuits was developed to minimize the adverse effects of stray electric fields created by the potentials in the metal interconnections. The process is compatible with silicon gate technology. n-doped polycrystalline silicon was used for all the gates and the shield. The effectiveness of the shield was demonstrated by constructing a special field plate over certain transistors. The threshold voltages obtained on a oriented silicon substrate ranged from 1.5 to 3 V for either channel. Integrated inverters performed satisfactorily from 3 to 15 V, limited at the low end by the threshold voltages and at the high end by the drain breakdown voltage of the n-channel transistors. The stability of the new structure with an n-doped silicon gate as measured by the shift in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C-V</tex> curve under 200°C ± 20 V temperature-bias conditions was better than conventional aluminum gate or p-doped silicon gate devices, presumably due to the doping of gate oxide with phosphorous. The advantages of the new structure are: avoidance of field inversion, elimination of guard rings, and thinner and more stable oxides.

The Resistivity Change due to ESR of Donor Electrons in P-Doped Silicon at Intermediate Region of Impurity Conduction. I

The electron spin resonance in phosphorus doped silicon belonging to the intermediate region of impurity conduction, was detected by resistivity change at 24 GHz microwave frequency. Two types of the resonance were observed. The one makes the resistivity increase, and the other makes the resistivity decrease at resonance. These two types of resonance are considered to be due to the electrons belonging to the relatively high and low concentration regions of inhomogeneously distributed impurities in the crystal. At the intermediate region of impurity conduction, these two regions are considered to coexist in a crystal. It is shown that the resonance of electrons belonging to these two regions, can separately be detected by the type of experiments described in the paper.

Radiation-Produced Absorption Bands in Silicon: Piezospectroscopic Study of a Group-V Atom-Defect Complex

A series of sharp new infrared-absorption bands produced by high-energy-electron irradiation in phosphorus- and arsenic-doped float-zone-refined silicon is reported. In P-doped silicon, the dominant band is at 1150 ${\mathrm{cm}}^{\ensuremath{-}1}$, with associated weaker bands at 1310, 970, 1000, 1025, 1040, and 1450 ${\mathrm{cm}}^{\ensuremath{-}1}$. In As-doped silicon, the corresponding bands are at 1260 ${\mathrm{cm}}^{\ensuremath{-}1}$ and 1480, 1080, 1110, 1135, 1160, and 1650 ${\mathrm{cm}}^{\ensuremath{-}1}$. The spectra recover in both materials at \ensuremath{\sim}140\ifmmode^\circ\else\textdegree\fi{}C. Uniaxial-stress studies of these bands in oriented single crystals with polarized light are described. The results cannot be fit to the usual "piezospectrospic" classification of Kaplyanskii and Runciman. A model is presented which identifies the spectra as electronic transitions from the orbital singlet ground state of a single anistropic donor defect to a manifold of bound large-orbit effective-mass excited states. Extension of the Kaplyanskii classification to include the accidental degeneracy inherent in the effective-mass excited states in silicon explains the stress results. The symmetry of the defect is deduced to be monoclinic II. It is deduced that one or more group-V atoms are involved in the defect, but a microscopic identification of the defect is not possible.

Electron and neutron irradiation of boron and phosphorus-doped silicon at 80°K

Abstract Conductivity and Hall effect measurements have been made on boron and phosphorus-doped silicon which had been irradiated at 80°k either in a nuclear reactor or with 2 Mev electrons. For the boron-doped samples a significant carrier removal rate attributed to the 10B(n, α)7Li reaction was observed. The carrier removal rates in electron irradiated B and P-doped samples were much smaller than predicted by a calculation based upon one carrier removed for each displacement produced. On the other hand, the fast and thermal neutron carrier removal rates were consistent with such a hypothesis, and it is suggested that the defects introduced by neutron irradiation are small complexes with associated levels deep in the forbidden gap. It is suggested that electron irradiation produces primarily neutral vacancies with levels so close to the valence band that they have no effect on the carrier removal rates in either B or P-doped silicon.

Electronic Structure of Sodium-Ammonia Solutions by Nuclear Magnetic Resonance

Knight shifts (ΔH) of the N14 and Na23 nuclear magnetic resonances have been observed in liquid sodium-ammonia solutions at 7000 gauss as a function of the mole ratio R=(moles NH3)/(moles Na) for 10⪝R ⪝1000. The Knight shifts decrease with increasing R and for R≈10, ΔH(N14)≈4, ΔH(Na23)≈1 gauss. The experimental results in these variable composition solutions are conveniently discussed in terms of P(N14) and P(Na23), the average hyperfine contact densities of N14 and Na23 nuclei at an unpaired electron. P(N14) and P(Na23) were estimated from K–NH3 paramagnetic susceptibility data and the ΔH's. For 50&amp;lt;R&amp;lt;400, P(Na23)=5–3×10—3 P0(Na23) where P0(Na23) is the contact density in an isolated sodium atom. In this concentration range we conclude the odd electrons move in highly expanded orbitals about Na+ ions similar to those appropriate to tetrahedrally bonded P+ ions in P-doped silicon where a similar reduction in the contact hyperfine density is found. Marked electron condensation on Na+ ions occurs at R⪝50 where P(Na23) and the electrical conductivity increase rapidly. P(N14)≈0.1 P0(N14) and is independent of R. H1Knight shifts were too small to detect.