- Email: [email protected]
The dopant density and temperature dependence of hole mobility and resistivity in boron doped silicon
World Abstracts on Microelectronics and Reliability
197
Electron. 21, 1123 (1978). A number of cautionary measures have been found necessary in applying the layer stripping/ four-point probe method to profiling thin epitaxial, ionimplanted and diffused layers. To minimize penetration of the layer by the probe, and carrier injection effects, low probe pressure must be used in conjunction with checks on the voltages developed between the current (outer) probes and the potential (inner) probes. Surface depletion in nlayers results in an apparent translation of the measured profile towards the surface, and for ion-implanted layers further results in a systematic distortion of the profile. These comments apply equally to layer stripping/Halleffect profiling techniques.
The phonon-mediated intervalley electron-electron interaction in silicon. M. J. KELLY. Solid State Commun. 27, 717
Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique. J. MULLER, H. BERNT and H. REICHL.
1133 (1978). Most papers covering metal-semiconductor ohmic contact theory which have been published up to date consider systems with homogeneous impurity concentration in the semiconductor. However, there are techniques of ohmic contact formation on nondegenerate semiconductor where only a very shallow surface layer is impurity enriched. In this paper a model of such contacts is proposed and a simple approximate analytical expression for the specific resistivity is derived. If the impurity concentration in the surface layer is very high, the contact specific resistivity is essentially proportional to N~:, NB being the semiconductor substrate impurity concentration. To make a good ohmic contact, it is sufficient that the width of the heavily doped surface layer be equal to the equilibrium contact depletion region width. Any further enlargement of the enriched layer practically does not influence the total sample resistance due to the dominant share of the semiconductor body resistance. Experimental results confirm these conclusions qualitatively.
Solid-St. Electron. 21, 999 (1978). A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.
Conduction properties of lightly doped, polycrystalline silicon. GEORGE J. KORSH and RICHARD S. MULLER. SolidSt. Electron. 21, 1045 (1978). A hyperbolic-sine relationship describing the current-voltage characteristics of lightlydoped, n-type polycrystalline silicon films is derived. The derivation is based on a previous model which assumes that electron-trapping states exist at the grain boundaries of the polycrystalline film. The trapped electrons cause a surface-depletion zone and a potential barrier at each grain boundary. Electrons are transported over the barriers by thermionic emission. Conduction measurements carried out on commercially prepared samples are in good agreement with the theory developed both in voltage and temperature dependence. The model parameters obtained from conduction measurements correspond reasonably well with values inferred from scanning electron micrographs.
The dopant density and temperature dependence of hole mobility and resistivity in boron doped silicon. SHENG S. LI. Solid-St. Electron. 21, 1109 (1978). Theoretical expressions for computing resistivity and conductivity mobility of holes as functions of dopant density and temperature have been derived for boron-doped silicon. The model is applicable for dopant densities from 10 ~3 to 3 z 10~8cm 3 and temperature between 100 and 400 K. Using a 3-band [i.e. heavy-hole, light-hole and the spin orbit splitting (SO) band] model, the hole mobility was calculated by properly combining the contributions from scattering by lattice phonons, ionized impurities and neutral impurities. In addition, the effects of hole-hole (h hi scattering and nonparabolicity of valence bands wcre taken into account in the mobility formulation. To verify our theoretical calculations, resistivity measurements on nine boron-doped silicon slices with dopant densities from 4.5 × 1014 to 3.2 x 10~Scm 3 were performed for l 0 0 < T < 4 0 0 K , using planar square-array test structure. Agreement between our calculated and measured resistivity values was within 6% over the entire range of dopant density and temperature studied here. Excellent agreement (within _+5°/,,) between our calculated hole mobility values and those of Wagner was obtained for NA < 1017 cm 3 for boron-doped silicon, while discrepancies were found for boron densities greater than 10 ~7 cm 3. This discrepancy is attributed to neglecting the effect of deionization of boron impurities at higher dopant densities by Wagner (i.e. assuming hole density is equal to the total boron density).
(1978). A tight-binding formulation is used to estimate both the electron-phonon matrix element and the intervalley phonon-mediated exchange interaction in bulk silicon. The resulting interactions are about an order of magnitude too small to be able to account, of their own, for the broken symmetry states observed inversion layers at the Si/SiO2 interface, where the selection rules are relaxed and other modes are available to enhance the interactions.
Metal-n-type semiconductor ohmic contact with a shallow N + surface layer. R. S. PoPOWC. Solid-St. Electron. 21,
Elastic and inelastic scattering of electrons by vibrating impurities in semiconductors. AKIRA SUZUKI and D. G. FROOD. J. Phys. Chem. Solids 39, 1099 (1978). Elastic and inelastic scattering of conduction electrons by vibrating ionized impurities in valence semiconductors is investigated. For elastic scattering, the modification of the Brooks Herring formula arising from impurity vibrations is unimportant for all conceivable electron temperatures and door concentrations. Similarly, for inealstic (one-phonon) processes, the change in electron phonon relaxation time (or in electron lattice coupling constant) arising from vibrations of the ionized centres is entirely negligible.
Carrier collection in a semiconductor quantum well. H. SHICHIJO, R. M. KOLBAS.N. HOI,ONYAK,Jr, R. D. DtJpu~s and P. D. DAPKUS. Solid St. Commun. 27, 1029 (1978). Data are presented showing that a GaAs quantum well, sandwiched between two epitaxial AlxG1 xAs (x ~ 0.4) confining layers, loses its effectiveness as a collector of excess carriers and as a source of recombination radiation for well dimensions L : < 100A. It is shown that this behavior is expected because of the difficulty in scattering carriers to the bottom of the quantum well as 1,: --* Ip, the path length for scattering (LO phonon).
Nucleation of electron-hole droplets swirl defects in silicon. Y. SHIRAKI and H. NAKAsHIMa. Solid St. Commun. 27, 1033 (1978). Electron hole droplets (EHDsl are revealed to be formed more preferentially in the defective area than in the defect-free area in silicon with swirl defects. That is, lattice defects which cause swirl defects act as nucleation centers of droplets more effectively than shallow-level impurity atoms. Luminescence intensity profile of droplets on the sample surface is found to correspond well to the swirl pattern and EHD and bound exciton peak intensities are rather competitive, while luminescence intensity due to free excitons is almost homogeneous in the sample.
197
Electron. 21, 1123 (1978). A number of cautionary measures have been found necessary in applying the layer stripping/ four-point probe method to profiling thin epitaxial, ionimplanted and diffused layers. To minimize penetration of the layer by the probe, and carrier injection effects, low probe pressure must be used in conjunction with checks on the voltages developed between the current (outer) probes and the potential (inner) probes. Surface depletion in nlayers results in an apparent translation of the measured profile towards the surface, and for ion-implanted layers further results in a systematic distortion of the profile. These comments apply equally to layer stripping/Halleffect profiling techniques.
The phonon-mediated intervalley electron-electron interaction in silicon. M. J. KELLY. Solid State Commun. 27, 717
Measurement of minority carrier lifetime and diffusion length in silicon epitaxial layers by means of the photocurrent technique. J. MULLER, H. BERNT and H. REICHL.
1133 (1978). Most papers covering metal-semiconductor ohmic contact theory which have been published up to date consider systems with homogeneous impurity concentration in the semiconductor. However, there are techniques of ohmic contact formation on nondegenerate semiconductor where only a very shallow surface layer is impurity enriched. In this paper a model of such contacts is proposed and a simple approximate analytical expression for the specific resistivity is derived. If the impurity concentration in the surface layer is very high, the contact specific resistivity is essentially proportional to N~:, NB being the semiconductor substrate impurity concentration. To make a good ohmic contact, it is sufficient that the width of the heavily doped surface layer be equal to the equilibrium contact depletion region width. Any further enlargement of the enriched layer practically does not influence the total sample resistance due to the dominant share of the semiconductor body resistance. Experimental results confirm these conclusions qualitatively.
Solid-St. Electron. 21, 999 (1978). A new method for the determination of minority carrier lifetime and diffusion length in thin silicon epitaxial layers was developed. Using a transparent MIS structure the surface recombination velocity was reduced below 25 cm/s. This method makes possible to determine minority carrier lifetime and also diffusion length much greater than the thickness of the epitaxial layer.
Conduction properties of lightly doped, polycrystalline silicon. GEORGE J. KORSH and RICHARD S. MULLER. SolidSt. Electron. 21, 1045 (1978). A hyperbolic-sine relationship describing the current-voltage characteristics of lightlydoped, n-type polycrystalline silicon films is derived. The derivation is based on a previous model which assumes that electron-trapping states exist at the grain boundaries of the polycrystalline film. The trapped electrons cause a surface-depletion zone and a potential barrier at each grain boundary. Electrons are transported over the barriers by thermionic emission. Conduction measurements carried out on commercially prepared samples are in good agreement with the theory developed both in voltage and temperature dependence. The model parameters obtained from conduction measurements correspond reasonably well with values inferred from scanning electron micrographs.
The dopant density and temperature dependence of hole mobility and resistivity in boron doped silicon. SHENG S. LI. Solid-St. Electron. 21, 1109 (1978). Theoretical expressions for computing resistivity and conductivity mobility of holes as functions of dopant density and temperature have been derived for boron-doped silicon. The model is applicable for dopant densities from 10 ~3 to 3 z 10~8cm 3 and temperature between 100 and 400 K. Using a 3-band [i.e. heavy-hole, light-hole and the spin orbit splitting (SO) band] model, the hole mobility was calculated by properly combining the contributions from scattering by lattice phonons, ionized impurities and neutral impurities. In addition, the effects of hole-hole (h hi scattering and nonparabolicity of valence bands wcre taken into account in the mobility formulation. To verify our theoretical calculations, resistivity measurements on nine boron-doped silicon slices with dopant densities from 4.5 × 1014 to 3.2 x 10~Scm 3 were performed for l 0 0 < T < 4 0 0 K , using planar square-array test structure. Agreement between our calculated and measured resistivity values was within 6% over the entire range of dopant density and temperature studied here. Excellent agreement (within _+5°/,,) between our calculated hole mobility values and those of Wagner was obtained for NA < 1017 cm 3 for boron-doped silicon, while discrepancies were found for boron densities greater than 10 ~7 cm 3. This discrepancy is attributed to neglecting the effect of deionization of boron impurities at higher dopant densities by Wagner (i.e. assuming hole density is equal to the total boron density).
(1978). A tight-binding formulation is used to estimate both the electron-phonon matrix element and the intervalley phonon-mediated exchange interaction in bulk silicon. The resulting interactions are about an order of magnitude too small to be able to account, of their own, for the broken symmetry states observed inversion layers at the Si/SiO2 interface, where the selection rules are relaxed and other modes are available to enhance the interactions.
Metal-n-type semiconductor ohmic contact with a shallow N + surface layer. R. S. PoPOWC. Solid-St. Electron. 21,
Elastic and inelastic scattering of electrons by vibrating impurities in semiconductors. AKIRA SUZUKI and D. G. FROOD. J. Phys. Chem. Solids 39, 1099 (1978). Elastic and inelastic scattering of conduction electrons by vibrating ionized impurities in valence semiconductors is investigated. For elastic scattering, the modification of the Brooks Herring formula arising from impurity vibrations is unimportant for all conceivable electron temperatures and door concentrations. Similarly, for inealstic (one-phonon) processes, the change in electron phonon relaxation time (or in electron lattice coupling constant) arising from vibrations of the ionized centres is entirely negligible.
Carrier collection in a semiconductor quantum well. H. SHICHIJO, R. M. KOLBAS.N. HOI,ONYAK,Jr, R. D. DtJpu~s and P. D. DAPKUS. Solid St. Commun. 27, 1029 (1978). Data are presented showing that a GaAs quantum well, sandwiched between two epitaxial AlxG1 xAs (x ~ 0.4) confining layers, loses its effectiveness as a collector of excess carriers and as a source of recombination radiation for well dimensions L : < 100A. It is shown that this behavior is expected because of the difficulty in scattering carriers to the bottom of the quantum well as 1,: --* Ip, the path length for scattering (LO phonon).
Nucleation of electron-hole droplets swirl defects in silicon. Y. SHIRAKI and H. NAKAsHIMa. Solid St. Commun. 27, 1033 (1978). Electron hole droplets (EHDsl are revealed to be formed more preferentially in the defective area than in the defect-free area in silicon with swirl defects. That is, lattice defects which cause swirl defects act as nucleation centers of droplets more effectively than shallow-level impurity atoms. Luminescence intensity profile of droplets on the sample surface is found to correspond well to the swirl pattern and EHD and bound exciton peak intensities are rather competitive, while luminescence intensity due to free excitons is almost homogeneous in the sample.