Lattice Temperature Effects Research Articles

EFFECTS OF LATTICE TEMPERATURE IN MOSFET ANALYSIS UNDER NON‐ISOTHERMAL CONDITIONS

Effects of lattice temperature on MOSFET characteristics and a rough distribution of carrier temperature, are studied using a non‐isothermal device simulator which also includes the effect of temperature gradient on the current density. To clarify the mechanism of the increase in lattice temperature, the source of heat generation is investigated. We have confirmed that the increase in lattice temperature results mainly from the generation of Joule heat, representing the product of the electric field and the electron current density. We also found that, as the gate length becomes short, the lattice temperature rises exponentially. In addition, it is found that the lattice temperature shows a localized increase of 77 degrees under normal biasing conditions in the MOSFET with a gate length of 0.5[ μ m].

Photothermal reflectance investigation of processed silicon. II. Signal generation and lattice temperature dependence in ion-implanted and amorphous thin layers

Photothermal reflectance investigations as a function of temperature of various forms of silicon (crystalline, ion-implanted, amorphous) are reported largely in the thermal wave regime (low-modulation frequencies and large laser beam spot sizes). The observed results have been explained by a thermal wave model that has been extended to include the effect of lattice temperature. The influence of substrate on the observed signal has been examined in light of the temperature and frequency dependence of the thermal diffusion length. The possible application of the technique to depth-profiling studies, and to the investigation of ion-implanted semiconductors, is discussed.

Laser-induced magneto-optical transitions from deep levels in n-InSb

We present a novel means for detecting and studying deep levels in high purity n-InSb with extremely sensitive magneto-optical techniques, combining sampling oscilloscope and lock-in amplifier methods. Oscillatory photoconductivity behavior in InSb has been investigated previously under a variety of conditions and in both n- and p-type samples. However, to our knowledge, no evidence has ever been presented for oscillatory magnetophotoconductivity (MPC) in n-InSb (or in any other semiconductor) caused by electron transitions from deep levels to the conduction band Landau levels. These studies allow a more precise determination and sensitive detection of deep levels through a more direct means than has been previously possible. We observe a resonant structure in the CO2 laser-induced MPC at liquid helium temperatures in n-InSb which is periodic in the inverse magnetic field and whose amplitude increases with the magnetic field. This behavior is typical for resonances involving Landau levels. The effect of lattice temperature, laser intensity, photon energy, and light polarization on the MPC is studied. The amplitude of this resonant structure saturates at moderate intensities (∼30 W/cm2) and shows no polarization dependence (for e⊥B and e∥B). These and other results indicate the presence of a deep level ≂74 meV below the conduction band edge (Eg ≂235 meV). Using a CO laser, a resonant structure is also observed from another deep level, ≂170 meV below the band edge. These deep levels could be caused by either lattice defects or residual impurities. Other structures observed with the CO2 laser are identified with LO phonon-assisted cyclotron resonance harmonic transitions within the conduction band, and two-photon magnetoabsorption interband transitions. ufoff

Hot-electron emission from silicon into silicon dioxide

Recent progress in the study of hot-electron emission from silicon into silicon dioxide is discussed. Experimental techniques include avalanche injection using gated diodes and MOS capacitors, nonavalanche injection using IGFET structures with an underlying supply p - n junction, and optically induced injection using silicon-gate IGFET structures. IGFET structures allow the fields in the SiO 2 layer and in the silicon depletion region to be varied independently. In addition, IGFET structures of reentrant geometry allow absolute emission probabilities of the hot electrons to be determined. Such absolute emission characteristics are useful not only for designing silicon devices but also for quantitative testing of theoretical models of the emission process. Several mechanisms of importance in the emission process have been identified. These are the Schottky lowering of the emission barrier, the scattering of hot electrons in the image-force potential well in the SiO 2 layer, the tunneling of hot electrons, and the effect of lattice temperature on electron heating. There is also experimental evidence of the dependence of the hot-electron distribution on electric field gradient. At present, only phenomenological models based on the lucky-electron concept have been developed to the point where quantitative comparison with experimental results is possible. The essential features of these models are discussed.

Effect of donor density and temperature on the performance of stabilized transferred-electron devices

A large-signal analysis is used to discuss the effect of lattice temperature and temperature gradients on the RF behavior of stabilized transferred-electron devices. The influence of the value of donor density and density gradients upon RF conversion efficiency is also discussed. It is shown that efficiency can be improved if either the heat sink is located at the anode or the donor density is increased near the anode end.

Behaviour of silicon pn junctions at temperatures between 4-2 and 300° K†

This paper presents the results of an investigation into the effect of lattice temperature on the breakdown voltage of silicon pn junctions. Measurements have been made over the temperature range 4-2-300° K using devices with nominal breakdown voltages from 8 to 13 v. Results show that the influence of temperature can be separated into three distinct temperature intervals. For temperatures greater than 100° K the carrier mean free path is the controlling factor of the ionization rate and causes the voltage to decrease with decrease of temperature. At low temperatures (less than 30° k) the breakdown voltage increases with cooling because freeze out of carriers in the base allows a significant voltage to be developed across this region. Calculations involving this voltage drop enable the field required for ionization of impurities to be evaluated. In the intermediate temperature range traps are observed by studying microplasma noise and these appear to influence the ionization rate. In addition to the break...

The Effect of Temperature on the Ionization Coefficient in Silicon†

The avalanche breakdown of p-n junction diodes across their space charge regions is known to be analogous to the Townsend mechanism for gases. Electric charge carriers, which gain sufficient energy from the field, are able to produce secondary electron-hole pairs. Both the holes and the electrons can themselves have ionizing collisions and thus the process leads to an avalanche. An important factor, controlling the breakdown, is the ionization coefficient a, defined as the number of electron-hole pairs produced by a carrier moving unit distance in the direction of the field. This paper presents the results of nn investigation into the effect of lattice temperature on the ionization coefficient. This has been achieved by observing the breakdown voltage of a range of silicon diodes with either step or linear graded junctions, and applying simple and well-known relationships between ionization coefficient and breakdown voltage. Measurements have been made over the temperature range 77 to 400°K, and for field strengths from 4 to 9 × 105 volts/cm. Results show the ionization to become more efficient with decrease in temperature over this range of field strength. Temperature is found to have a greater effect at the lower field strength. This is shown to be consistent with modern theory.

Anomalous Penetration of Heavy Ions of keV Energies in Monocrystalline Tungsten

An electromagnetic separator was used to bombard single crystals of tungsten with 40-kev /sup 135/Xe ions to study the effect of crystallographic orientation on the range distribution of the ions. The results agree with theoretical predictions for bcc lattices. Plots of the residual activity against the depth showed a penetrating tail'' of the range distribution occurring above a few hundred mu g/cm/sup 2/ in addition to the main distribution. Two supplementary experiments were performed to study effect of lattice temperature and incident energy along the direction on the tail of the distribution. (L.B.S.)