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Memory traps in MNOS diodes measured by thermally stimulated current
World Abstracts on Microelectronics and Reliability topography and by the known etch rate, a general equation of motion of the etched surface has been derived, indispensable for interpretation of etching results. After analysis of known factors exerting influence on the etching of semiconductor materials, there was proposed a manner of selecting and checking conditions of etching with a view to ensuring sufficient dependence of the etch rate on the concentration of electrically active impurities in a semiconductor, and reproducibility of results in relation to Si and GaAs. A detailed procedure for determining distributions of impurities concentration is illustrated on the example of silicon epitaxial films n/n + and p/p+, as also diffusive junctions p-n and I h. The results thus obtained are compared with the results of investigation of analogous material by the method of characteristics C (1,/) of M - S and p-n junctions and of conductance by means of a four-point probe.
Mixed conduction in Cr-doped GaAs. D. C. LooK. J. Phys. Chem. Solids. 36, 1311 (1975). Hall-effect and magnetoresistance measurements have been carried out in G a A s : C r functions of magnetic field strength (B = (~18 kG) and temperature (T = 125-420°K). Independent solutions for the mobilities, #, and Pr and the carrier concentrations, n and p, are obtained from the basic mixed-conductivity equations. These quantities, as well as the intrinsic carrier concentration, n~, are then calculated as a function of temperature for one sample, and subsequent analysis yields the following values in the range T = 360-420K: an acceptor (presumably Cr) energy E,4 = 0.69 + 0.02eV (from the valence band); the bandgap energy Eg = EgO + ~ T, with Eg o = 1.48 + 0.02 eV, _~ 3.2 × 1 0 - 4 e V / K ; /2n = 2700 + 100cm2/V sec, decreasing slightly with temperature; #v = 350 + 50cm2/ V sec; and an acceptor-to-donor concentration ratio, NA/N o ~- 8. The electron mobility appears to be limited by neutral impurity scattering, with NA m 2 × 10~6cm -3. Several other samples were also investigated but as a function of temperature only (at B = 0). At room temperature both positive (p-type) and negative (n-type) Hall coefficients were observed.
Drift velocities of carriers in degenerate semiconductors. WAFIK A. WASSEF Int. J. Electronics 39 (4), 433 (1975). The parameters of a general distribution functiorb of carriers in semiconductors are determined by imposing some constraints on the total energy of the system of carriers. The correlation between these parameters indicates that both the temperature and the Fermi level of carriers must change with the applied field in order that the total energy of carriers assumes a stationary value. An expression for the drift velocity of carriers in degenerate semiconductors in terms of these parameters is given.
Memory traps in MNOS diodes measured by thermally stimulated current. TERUAKI KATSUBE, YOSHIO ADACHI and TOSmAKI IKOMA. Solid State Electronics 19, 11 (1976): Thermally stimulated current was measured to determine trap distribution and charging and discharging mechanisms in a Metal-Nitride-Oxide-Semiconductor (MNOS) diode with 16A oxide thickness. By changing gate voltage, heating rate and the initial flat-band voltage, the memory traps near the nitride-oxide interface were separated from the others. The general formula was derived for the thermally stimulated current in an M N O S diode and was applied to obtain the trap distribution as well as effective emission time constants. The results indicate that the memory traps are distributed 50 A deep into the nitride film from the nitride-oxide interface. The energy level lies at around 2.55 eV from the bottom of the nitride conduction band. The charging and discharging mechanism is the cascade connection of tunneling and thermal excitation or trapping. The obtained trap distribu-
107
tion and the charge transfer mechanism are successful for interpreting the write-in and retention characteristics.
Investigation of the transition from tunneling to impact ionization multiplication in silicon p-n junction. WIESLAW A. LUKASZEK, ALDERT VAN DER ZEIL and EUGENE R. CHENETTE. Solid State Electronics 19, 57 (1976). White noise spectra of diodes breaking down between 1.5 and 5 V have been used to investigate the details of the transition from tunneling to avalanche breakdown in silicon p n junctions. It is found that the transition and carrier multiplication in these junctions is dominated by the influence of the threshold energies for ionization. Because this influence is not explicitly taken into account in the existing theories of carrier multiplication and noise, they are not applicable to low breakdown voltage diodes. Consequently, a multiplication onset model and alternate schemes for calculating the DC multiplication and noise in low breakdown voltage diodes are developed. Analysis of the noise data indicates that the threshold energies for ionization depend slightly on junction widths and, for the diodes employed in this study, range between 1.66-1.9 eV for electrons and 1.79 2.04eV for holes. The m i n i m u m distance between ionizing collisions is found to range from 190 to 240A for electrons and 200 to 250A for holes. Application of the threshold energies for ionization to the multiplication onset model permits evaluation of the doping densities on both sides of the step junctions. F r o m it, it is determined that the solubility of aluminium in silicon is N~ = 9.5 + 0.5 x I0~Scm 3.
Theoretical analysis of the influence of an ~h junction on operation of semiconductor devices. ANDRZEJ KASSUR. Electron Technology, Warsaw 8, (1), 13 (1975). In the paper, the static and dynamic characteristics of diode structures with two p n and ~ h junctions have been analyzed. It is assumed that the principle of neutrality is fulfilled and it is employed the formalism of potential tp. From the general formulae obtained in the paper one can obtain, after the additional reductions, the majority of the known so far relationships describing the static and dynamic characteristics of (p n), (p-n) (I-h) diodes and (Nh)-(I h) resistors with both a long and short base.
Diffusion of phosphorus into silicon using phosphine gas as a source. S. N. GHOSH DAST1DAR. Solid State Technology p. 37 (Nov. 1975). Diffusion experiments were conducted using a gaseous dopant (PH3) into silicon in an open tube system. The findings of these experiments with respect to resistivity and diffusion depth are presented for different gas velocities, temperatures of diffusion and diffusion times. It is possible to achieve reproducible p~ of 15 o h m s per square with acceptable tolerance limits ( + 5°/,;) with proper choice of the gas flow parameter and a suitable program cycle. The process yields a higher concentration gradient at the p-n junction than other diffusion methods used for phosphorous diffusion. This process is, therefore, best suitable for emitter diffusion of switching transistors.
Investigation of polycrystailine silicon layers by electron microscopy and X-ray diffraction. S. HORIUCm. Solid State Electronics 18, 1111 (1975). The structure of polycrystalline Si layers deposited by pyrolysis of silane in a hydrogen ambient has been investigated by replica electron microscopy and X-ray diffraction. When the gas flow ratio (SiH4/Hz) is 3.64 × 10 -4, the temperature region below 900°C is a surface reaction control region and the activation energy of the chemical surface reaction rate is 1.6eV. The temperature range above 900°C is a mass transfer region and the deposition rate is about 500 A/min. The grains become larger and the texture of the surface of the poly Si layers becomes coarser with the deposition temperature. Some phase change was found to occur
Mixed conduction in Cr-doped GaAs. D. C. LooK. J. Phys. Chem. Solids. 36, 1311 (1975). Hall-effect and magnetoresistance measurements have been carried out in G a A s : C r functions of magnetic field strength (B = (~18 kG) and temperature (T = 125-420°K). Independent solutions for the mobilities, #, and Pr and the carrier concentrations, n and p, are obtained from the basic mixed-conductivity equations. These quantities, as well as the intrinsic carrier concentration, n~, are then calculated as a function of temperature for one sample, and subsequent analysis yields the following values in the range T = 360-420K: an acceptor (presumably Cr) energy E,4 = 0.69 + 0.02eV (from the valence band); the bandgap energy Eg = EgO + ~ T, with Eg o = 1.48 + 0.02 eV, _~ 3.2 × 1 0 - 4 e V / K ; /2n = 2700 + 100cm2/V sec, decreasing slightly with temperature; #v = 350 + 50cm2/ V sec; and an acceptor-to-donor concentration ratio, NA/N o ~- 8. The electron mobility appears to be limited by neutral impurity scattering, with NA m 2 × 10~6cm -3. Several other samples were also investigated but as a function of temperature only (at B = 0). At room temperature both positive (p-type) and negative (n-type) Hall coefficients were observed.
Drift velocities of carriers in degenerate semiconductors. WAFIK A. WASSEF Int. J. Electronics 39 (4), 433 (1975). The parameters of a general distribution functiorb of carriers in semiconductors are determined by imposing some constraints on the total energy of the system of carriers. The correlation between these parameters indicates that both the temperature and the Fermi level of carriers must change with the applied field in order that the total energy of carriers assumes a stationary value. An expression for the drift velocity of carriers in degenerate semiconductors in terms of these parameters is given.
Memory traps in MNOS diodes measured by thermally stimulated current. TERUAKI KATSUBE, YOSHIO ADACHI and TOSmAKI IKOMA. Solid State Electronics 19, 11 (1976): Thermally stimulated current was measured to determine trap distribution and charging and discharging mechanisms in a Metal-Nitride-Oxide-Semiconductor (MNOS) diode with 16A oxide thickness. By changing gate voltage, heating rate and the initial flat-band voltage, the memory traps near the nitride-oxide interface were separated from the others. The general formula was derived for the thermally stimulated current in an M N O S diode and was applied to obtain the trap distribution as well as effective emission time constants. The results indicate that the memory traps are distributed 50 A deep into the nitride film from the nitride-oxide interface. The energy level lies at around 2.55 eV from the bottom of the nitride conduction band. The charging and discharging mechanism is the cascade connection of tunneling and thermal excitation or trapping. The obtained trap distribu-
107
tion and the charge transfer mechanism are successful for interpreting the write-in and retention characteristics.
Investigation of the transition from tunneling to impact ionization multiplication in silicon p-n junction. WIESLAW A. LUKASZEK, ALDERT VAN DER ZEIL and EUGENE R. CHENETTE. Solid State Electronics 19, 57 (1976). White noise spectra of diodes breaking down between 1.5 and 5 V have been used to investigate the details of the transition from tunneling to avalanche breakdown in silicon p n junctions. It is found that the transition and carrier multiplication in these junctions is dominated by the influence of the threshold energies for ionization. Because this influence is not explicitly taken into account in the existing theories of carrier multiplication and noise, they are not applicable to low breakdown voltage diodes. Consequently, a multiplication onset model and alternate schemes for calculating the DC multiplication and noise in low breakdown voltage diodes are developed. Analysis of the noise data indicates that the threshold energies for ionization depend slightly on junction widths and, for the diodes employed in this study, range between 1.66-1.9 eV for electrons and 1.79 2.04eV for holes. The m i n i m u m distance between ionizing collisions is found to range from 190 to 240A for electrons and 200 to 250A for holes. Application of the threshold energies for ionization to the multiplication onset model permits evaluation of the doping densities on both sides of the step junctions. F r o m it, it is determined that the solubility of aluminium in silicon is N~ = 9.5 + 0.5 x I0~Scm 3.
Theoretical analysis of the influence of an ~h junction on operation of semiconductor devices. ANDRZEJ KASSUR. Electron Technology, Warsaw 8, (1), 13 (1975). In the paper, the static and dynamic characteristics of diode structures with two p n and ~ h junctions have been analyzed. It is assumed that the principle of neutrality is fulfilled and it is employed the formalism of potential tp. From the general formulae obtained in the paper one can obtain, after the additional reductions, the majority of the known so far relationships describing the static and dynamic characteristics of (p n), (p-n) (I-h) diodes and (Nh)-(I h) resistors with both a long and short base.
Diffusion of phosphorus into silicon using phosphine gas as a source. S. N. GHOSH DAST1DAR. Solid State Technology p. 37 (Nov. 1975). Diffusion experiments were conducted using a gaseous dopant (PH3) into silicon in an open tube system. The findings of these experiments with respect to resistivity and diffusion depth are presented for different gas velocities, temperatures of diffusion and diffusion times. It is possible to achieve reproducible p~ of 15 o h m s per square with acceptable tolerance limits ( + 5°/,;) with proper choice of the gas flow parameter and a suitable program cycle. The process yields a higher concentration gradient at the p-n junction than other diffusion methods used for phosphorous diffusion. This process is, therefore, best suitable for emitter diffusion of switching transistors.
Investigation of polycrystailine silicon layers by electron microscopy and X-ray diffraction. S. HORIUCm. Solid State Electronics 18, 1111 (1975). The structure of polycrystalline Si layers deposited by pyrolysis of silane in a hydrogen ambient has been investigated by replica electron microscopy and X-ray diffraction. When the gas flow ratio (SiH4/Hz) is 3.64 × 10 -4, the temperature region below 900°C is a surface reaction control region and the activation energy of the chemical surface reaction rate is 1.6eV. The temperature range above 900°C is a mass transfer region and the deposition rate is about 500 A/min. The grains become larger and the texture of the surface of the poly Si layers becomes coarser with the deposition temperature. Some phase change was found to occur