The dominant mechanisms of charge-carrier scattering in lead telluride

The present status of the dominant mechanisms of charge-carrier scattering in lead telluride is analyzed critically. It is shown that the role of the Coulomb potential of the vacancies and the role of the deformation potential of acoustic phonons in carrier scattering in PbTe has been strongly overestimated in most existing studies. Futhermore, the role of optical phonons at high temperatures has been unjustifiably reduced to a polar component only. It is shown that, in addition to this mechanism, the deformation potential due to optical phonons, whose greatest contribution is at high carrier densities, also plays an important role in carrier scattering processes at temperatures in the range of room temperature. Fiz. Tekh. Poluprovodn. 31, 281–284 (February 1997)     

Water-enhanced negative bias temperature instability in p-type low temperature polycrystalline silicon thin film transistors

Water-enhanced degradation of p-type low temperature polycrystalline silicon thin film transistors under negative bias temperature (NBT) condition is studied. H₂O penetration into gate oxide network and the role of H₂O during NBT stress are confirmed and clarified respectively. To prevent H₂O diffusion, a combination of a layer of PECVD SiO₂ and a layer of PECVD Si₃N₄ as passivation layers are investigated, revealing that 100 nm SiO₂ and 300 nm Si₃N₄ can effectively block H₂O diffusion and improve device NBT reliability.     

Minority-charge-carrier mobility at low injection level in semiconductors

From the kinetic equations, the distribution functions for majority and minority charge carriers are obtained at a low injection level. For describing the electron-hole collisions, the Landau collision integral is used. The carrier scattering at ionized or neutral impurity and at acoustic phonons is taken into account. The majority-carrier distribution function is presented in the analytical form. The minority-carrier mobility is calculated and analyzed, and the features of its behavior at low temperatures are revealed. It follows from the developed theory that the hole mobility in an n-type material increases with doping and neutral-impurity concentration. This effect is attributed to mutual charge-carrier collisions and different effective masses of different-sign carriers.     

Calculation of the charge-carrier mobility in diamond at low temperatures

The discrepancies between the quasi-elastic and inelastic approaches to the calculation of the electron and hole mobilities in diamond at low temperatures when the carrier scattering from acoustic phonons becomes significantly inelastic have been numerically estimated. The calculations showed that the mobility described by a close-to-equilibrium distribution function differs several times from that obtained within the quasi-elastic approach even at 20 K. The results obtained are important for interpreting the low-temperature electrical experiments on high-purity diamond single crystals.     

Infrared tomography of the charge-carrier lifetime and diffusion length in semiconductor-grade silicon ingots

A nondestructive method for measuring the three-dimensional distribution of the charge-carrier lifetime and diffusion length in silicon ingots with a length of up to 1 m and a diameter as large as 0.3 m is presented. Physically, this method is based on infrared crossed-beam probing of an ingot with polished surface areas. One of the beams is repetitively pulsed, has a wavelength of 1.15–1.28 μm, and generates excess charge carriers in a rodlike zone along the beam trajectory in the ingot. Other beams are continuous and have longer wavelengths; these beams detect the temporal and spatial kinetics of excess charge carriers in a small portion of the rodlike zone and in the vicinity of it (the free-carrier absorption is measured). By virtue of the fact that the investigated zone is at a distance from the ingot surface, there is no need to consider the surface recombination. The capabilities of the method are demonstrated for an ingot with known spatial nonuniformity of the charge-carrier lifetime. Spatial resolution amounting to several millimeters was attained. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 1, 2001, pp. 40–47. Original Russian Text Copyright ? 2001 by Akhmetov, Fateev.     

Transient high level majority and minority carrier photocurrents in p-type silicon Schottky barrier diodes—II: Comparison with computer calculations

Computer calculations of majority and minority carrier transient current pulses in a totally depleted silicon diode are compared with experimental current pulse shapes obtained by light pulse excitation of the diode. Numerical solution of the transport equations permitted the roles of the field dependence of the carrier mobility and of the excitation depth of the exciting light pulse to be investigated. Improved agreement of the computer solution as compared to previously made analytical calculations, particularly under conditions of high electric field or high space charge, is found.     

Defects in annealed 1.5 MeV boron implanted p-type silicon

Effects of temperature and dosage on the evolution of extended defects during annealing of MeV ion-implanted Czochralski (CZ) p-type (001) silicon have been studied using transmission electron microcopy. Excess interstitials generated in a 1 10¹⁵ cm⁻²/1.5 MeV B⁺ implanted Si have been found to transform into extended interstitial {311} defects upon rapid thermal annealing at 800°C for 15 sec. During prolonged furnace annealing at 960°C for 1 h, some of the {311} defects grow longer at the expense of the smaller ones, and the average width of the defects seems to decrease at the same time. Formation of stable dislocation loops appears to occur only above a certain threshold annealing temperature (∼1000°C). The leakage current in diodes fabricated on 1.5 MeV B⁺ implanted wafers was found to be higher for a dosage of 1 10¹⁴cm⁻² and less, as compared to those fabricated with a dosage of 5 10¹⁴ cm⁻² and more. The difference in the observed leakage current has been attributed to the presence of dislocations in the active device region of the wafers that were implanted with the lower dosage.     

Carrier mobilities in silicon semi-empirically related to temperature,doping and injection level

From a review of different publications on the carrier mobilities in silicon, the authors propose an approximated calculation procedure which permits a quick and accurate evaluation of these mobilities over a large range of temperatures, doping concentrations and injection-levels.The proposed relations are well adapted to semiconductor device simulation becuase they allow short computation times.     

Isochronal annealing study of hydrogen interaction with implantation-induced point defects in p-type silicon

Isochronal annealing with zero and reverse bias applied to Schottky diodes was used to monitor the evolution of hydrogen interaction with point defects observed in hydrogen-implanted p-type silicon, i.e., divacancy (VV), carbon–oxygen interstitial pair (C_iO_i) and two levels at E_v+0.28 and E_v+0.50 eV. The VV and C_iO_i are passivated by hydrogen liberated from hydrogen-containing defects during annealing in the temperature range 90–150°C and reappear upon annealing above 180°C under reverse bias due to hydrogen liberation and its field drift. Two levels at E_v+0.50 and E_v+0.28 eV are ascribed to irradiation-induced and hydrogen-related defects, respectively.     

A theoretical explanation of the carrier lifetime as a function of the injection level in gold-doped silicon

An expression for the recombination rate in gold-doped silicon is derived taking into account both gold energy levels. This formula shows that the dominant energy level under high-injection conditions is not the midgap gold acceptor, but the gold donor level. The high-low injection lifetime ratio calculated with the derived expression is in good agreement with measured values. This indicates that lifetime and capture cross section measurements are consistent with each other. The relation between gold concentration and high-injection lifetime is calculated. The relative density of the neutral and the negatively and positively charged traps is shown as a function of the carrier injection level.     

Electrical measurement of electron and hole mobilities as afunction of injection level in silicon

The first experimental method to separately measure the hole and the electron mobilities as a function of the injection level is presented. The carrier mobilities are extracted from impulsive measurements of the resistance associated with a n⁺-ν-n ⁺ (p⁺-π-p⁺) structure, where the conductivity of the intermediate layer is controlled by the injection of an incorporated p-n junction diode. Two-dimensional numerical simulation is used to assess the accuracy of the proposed measurement technique. Experimental results obtained at room temperature on both n-type and p-type materials are presented and compared to existing analytical mobility models     

On the injection level dependence of the minority carrier lifetime in defected silicon substrates

In the literature several reports have indicated a strong increase of the minority carrier lifetime with injection level in defected single crystal and semi-crystalline silicon. These types of potentially low-cost materials are being developed for the photovoltaic industry. The lifetime increase, mainly observed at low injection levels, has usually been explained by the saturation of active traps with increasing injection level. However, a detailed experimental analysis of the recombination losses in materials showing this behavior, points to a strong local variation in the trap density, presumably associated with crystal microdefects. We demonstrate in this paper that the non-linearity of the recombination current at low illuminations observed in defected materials, can be explained by considering the recombination at grain boundaries and microdefects. The conditions are detailed under which the lifetime increases with injection level.     

Titanium in silicon as a deep level impurity

Titanium inserted in silicon by diffusion or during Czochralski ingot growth is electrically active to a concentration level of about 4 × 10¹⁴ cm^?3. Hall measurements after diffusion show conversion of lightly doped p type Si to n type due to a Ti donor level at E_C - 0.22 eV. In DLTS measurements of n⁺p structures this level shows as an electron (minority carrier) trap at E_C - 0.26 eV with an electron capture cross section of about 3 × 10^?15 cm² at 300°K. The DLTS curves also reveal a hole trap in the p type material. The e_p (300/T)² activation plot gives the level as E_V + 0.29 eV. The hole capture cross section is about 1.7 × 10^?17 cm² at 300°K and decreases with decreasing temperature and the corrected trap level becomes E_V = 0.26 eV. Ti in lightly doped (360 ohm-cm) n type material does not result in conversion to p type so this level is inferred also to be a donor.A Ti electrically active concentration of about 1.35 × 10¹³ cm^?3 in p type (N_A = 3.35 × 10¹⁵cm^?3) Si results in a minority carrier (electron) lifetime of 50 nsec at 300°K.     

Theoretical analysis of hall factor and hall mobility in p-type silicon

Using a two-band (i.e. heavy-hole and light-hole band) model and the relaxation time approximation, the Hall factor was calculated for the case of silicon doped with boron. Contributions from scattering by acoustical and optical phonons and by ionized and neutral impurities were considered. In addition, the effects of hole-hole scattering, as well as valence band nonparabolicity and anistropy were also taken into account. The scattering and anistropy factors were separately evaluated to emphasize their individual contributions to the Hall factor. Theoretical values of the Hall factor at 300 K vary between 0.882 and 0.714 over the dopant density ranges 10¹⁴ ≦ N_A ≦ 3 × 10¹⁸ cm^?3. Hall mobilities for p-type silicon were calculated and compared with published data 100 ≤ T ≤ 400 K and 10¹⁴ ≦ N_A ≦ 3 × 10¹⁸ cm^?3. The present model is limited to the case of uncompensated material and for the weak field in which μ_HB ? 1.     

Operation of a double heterojunction GaAs/AlGaAs injection laser with a p-type active layer in a strong magnetic field

Measurements of the energy shift of the laser emission and the threshold current of a double heterojunction GaAs/AlGaAs injection laser with a p-type active layer as a function of the magnetic field up to25 Tand atT = 6K and 40 K are presented. A simple expression is derived for calculation of the maximum of the gain curve, which coincides with the energy of the laser emission as a function of the magnetic field and the electronic scattering time. From the experimentally observed shift of the laser emission and the calculated maximum of the gain curve as a function of the magnetic field values for the carrier density at threshold, and for the electronic scattering time in the active layer at both temperatures have been obtained.     

Temperature dependence of resistivity and hole conductivity mobility in p-type silicon

A new method is employed to determine the temperature dependence of the resistivity and hole conductivity mobility of p-type silicon. This method involves the use of an aluminum-on-p-Si ohmic diode and a magnesium on p-Si Schottky barrier diode on the same silicon chip. The resistivity is determined from the Al/p-Si ohmic diode. The hole concentration is evaluated from the C-V data of the Mg/p-Si Schottky barrier diode. The conductivity mobility is then computed from the resistivity and hole concentration data. The following ranges are covered: 77–300 K, 0.4–100 ohm-cm and 5 × 10¹⁶?2 × 10¹⁴ holes/cm³ at room temperature.     

A model of the conductivity of p-type polycrystalline silicon with regard to current spreading in crystallites

A model of the conductivity of a p-type polycrystalline silicon film with current spreading in crystallites is considered. The model is self-consistent and describes fairly well the experimental data on conductivity and the piezoresistance effect in p-type polysilicon before and after current-pulse annealing. The conclusion is that the areas of electrical contacts between the crystallites are close to the geometrical areas between them; nevertheless, the current density in crystallites is not uniform.