W. Wiegmann

Bio: W. Wiegmann is an academic researcher from Bell Labs. The author has contributed to research in topics: Ionization. The author has an hindex of 1, co-authored 1 publications receiving 442 citations.

Ionization Rates of Holes and Electrons in Silicon

Abstract: The ionization rates of charge carriers in silicon have been measured and fit to the recent theoretical calculations of Baraff; in contrast, none of the existing published data could be fit to these theoretical curves The study has been made using microplasma-free junctions of demonstrably high, uniform local multiplication A new and considerably simplified approach to the problem of extracting the ionization rates from the multiplication data has been used By employing much more precise control of the electron and hole currents used to initiate the multiplication process, the hole ionization rate at electric fields less than 300 kV/cm is found to be more than an order of magnitude smaller than any previously published measurements Hole and electron ionization rates have been measured in the same junction and consequently in the identical scattering environment The threshold energy is determined to be ${E}_{g}\ensuremath{\le}{E}_{i}\ensuremath{\le}15{E}_{g}$, and the mean free path for scattering of high-energy electrons is $50 \AA{}\ensuremath{\le}{\ensuremath{\lambda}}_{e}\ensuremath{\le}70 \AA{}$ and for energetic holes $30 \AA{}\ensuremath{\le}{\ensuremath{\lambda}}_{h}\ensuremath{\le}45 \AA{}$ Measurement of ionization rates at various temperatures substantiates the assumption that the energy-loss mechanism is the emission of optical phonons In addition, significant differences of the electrical breakdown characteristics of microplasma-free junctions are discussed as well as their preparation

Large-signal analysis of a silicon Read diode oscillator

Abstract: This paper presents theoretical calculations of the large-signal admittance and efficiency achievable in a silicon p-n-v-ns Read IMPATT diode. A simplified theory is employed to obtain a starting design. This design is then modified to achieve higher efficiency operation as specific device limitations are reached in large-signal (computer) operation. Self-consistent numerical solutions are obtained for equations describing carrier transport, carrier generation, and space-charge balance. The solutions describe the evolution in time of the diode and its associated resonant circuit. Detailed solutions are presented of the hole and electron concentrations, electric field, and terminal current and voltage at various points in time during a cycle of oscillation. Large-signal values of the diode's negative conductance, susceptance, average voltage, and power-generating efficiency are presented as a function of oscillation amplitude for a fixed average current density. For the structure studied, the largest microwave power-generating efficiency (18 percent at 9.6 GHz) has been obtained at a current density of 200 A/cm2, but efficiencies near 10 percent were obtained over a range of current density from 100 to 1000 A/cm2.

Measurement of the ionization rates in diffused silicon p-n junctions

Abstract: An improved method is presented for calculating the ionization rates αn and αp from charge multiplication measurements on diffused silicon p-n junctions. The main features of this method are: The real impurity profile is approximated by an exponential function whose parameters are calculated from capacitance measurements; the ratio γ = αp/αn as a function of the electric field is calculated from multiplication measurements; the ionization rates are solved from the ionization integral for pure electron injection, taking the influence of the threshold energy into account. Measurements on narrow junctions agree with measurements on wide junctions by assuming a threshold energy of 1.8 eV for electrons, in agreement with the results of M oll and van O verstraeten .(1) The ionization rates differ from those of M oll and van O verstraeten (1) and of L ee , L ogan et al.(2) mainly because these authors neglect the influence of the threshold energy. The electron and hole data satisfy Chynoweth's law α(E) = α ∞ exp (−b/¦E¦), cm −1 with: for electrons α∞ = 7.03 × 105 cm−1 b = 1.231 × 106 V cm−1 for 1.75 × 105 ⩽ E ⩽ 6.0 × 105 V cm−1 for holes α∞ = 1.582 × 106 cm−1b = 2.036 × 106 V cm−1 for 1.75 × 105 ⩽ E ⩽ 4.0 × 105 V cm−1 and α∞ = 6.71 × 105 cm−1b = 1.693 × 106 V cm−1 for 4.0 × 105 ⩽ E ⩽ 6.0 × 105 V cm−1 Breakdown voltages are computed for high voltage p-n and p-i-n diodes. These are in good agreement with experiments, indicating the reliability of the ionization rates.

Bandgap Dependence and Related Features of Radiation Ionization Energies in Semiconductors

Abstract: The problems dealt with concern the production of electron‐hole pairs in a semiconductor exposed to high‐energy radiation. The goal is to develop a simple phenomenological model capable of describing the present experimental situation from the standpoint of yield, variance, and bandgap dependence. We proceed on the premise that e, the average amount of radiation energy consumed per pair, can be accounted for by a sum of three contributions: the intrinsic bandgap (EG), optical phonon losses r(ℏωR), and the residual kinetic energy (9/5) EG. The approach differs from prior treatments in the sense that the residual kinetic energy relates to a threshold for impact ionization taken to be 32EG in accordance with indications stemming from studies of avalanching in p‐n junctions. This model is subjected to three quantitative tests: (a) Fano‐factor variations are found to reflect the relative weight of phonon losses [K=r(ℏωR)/EG], but residual energy fluctuations govern the statistical behavior for K2 ≲0.3. An appl...

Monte Carlo simulation of transport in technologically significant semiconductors of the diamond and zinc-blende structures. I. Homogeneous transport

Abstract: Monte Carlo simulations of electron transport in seven semiconductors of the diamond and zinc-blende structure (Ge, Si, GaAs, InP, AlAs, InAs, GaP) and some of their alloys (Al/sub x/Ga/sub 1-x/As, In/sub x/Ga/sub 1-x/As, Ga/sub x/In/sub 1-x/P) and hole transport in Si were performed at two lattice temperatures (77 and 300 K). The model uses band structures obtained from local empirical pseudopotential calculations and particle-lattice scattering rates computed from the Fermi golden rule to account for band-structure effects. Intervalley deformation potentials significantly lower than those which have been previously reported are needed to reproduce available experimental data. This is attributed to the more complicated band structures, particularly around the L- and X-symmetry points in most materials. Satisfactory agreement is obtained between Monte Carlo results and some experiments. >