Drift Mobility Of Charge Carriers Research Articles

Photoluminescence and carrier drift mobility at the ferroelectric phase transitions

Abstract Some new photoluminescence bands and their intensity increase have been observed in SrTi03, PbTi03, Cd2Nb207 and PbMg1/3 Nb2/303 crystals at the temperatures near ferroelectric and structural phase transitions at the interband excitation. This phenomenon can be related to the carrier autolocalized state creation. The temperature dependence of the emission intensity correlates with the temperature dependence of the soft mode inverse frequency in SrTi03 near 110K and with the temperature dependence of the charge carrier drift mobility in PbMg1/3Nb2/303 at the diffuse phase transition.

Temperature dependence of carrier generation, and transport in p a r a-terphenyl above and below the 180 °K phase transition

Charge carrier drift mobilities have been measured in para-terphenyl single crystals by the transient photoconductivity method. In the a, b, and c′ crystal directions, room temperature electron mobilities were 0.34, 1.2, and 0.25 cm2 V−1 sec−1, respectively, and 0.80 cm2 ⋅V−1 sec−1 in the c′ direction for holes. Electron mobilities in the a, b direction followed a T−0.5 and T−0.7 dependence but for temperatures below the 180 °K phase transition, a T−2.5 dependence is followed. No discontinuity in the carrier mobility temperature dependence were observed. Hole photocurrents in all crystal directions could be measured at low temperatures. Possible mechanisms of carrier transport and carrier generation are discussed.

Charge carrier drift mobility in polycrystalline tetracene layers

The charge carrier drift mobility in tetracene layers was measured using the time-of-flight method. Free carriers were generated by short electron pulses. At electric fields E > 2 × 10 4V cm −1 the drift velocity of holes is constant, i.e. the drift mobility is proportional to the reciprocal electric field: μ h ∝ E −1.

Temperature dependence of drift mobility in the presence of trap-recombination centers

The effect of trap-recombination centers on the temperature dependence of the chargecarrier drift mobility μg in semiconductors is investigated both theoretically and experimentally. The temperature dependence μg(T) becomes steeper than the temperature dependence of the microscopic mobility μ(T) in the temperature range where Ed=Et ± 2κT (Ed is the demarcation level; Et is the level at which the centers occur). The dependence μg(T) is measured experimentally in CdS from the temperature dependence of the acoustic current. The experiments agree with the theoretical calculations.

Temperature dependence and anisotropy of charge carrier mobilities in durene

Very high charge-carrier drift mobilities have been measured in durene (1,2,4,5 tetramethyl benzene) single crystals by the transient-photoconductivity technique. In the crystal ($a, b$) plane both hole and electron mobilities are isotropic, 5 ${\mathrm{cm}}^{2}$/V sec and 8 ${\mathrm{cm}}^{2}$/V sec, respectively, at room temperature, and follow a ${T}^{\ensuremath{-}2.5}$ temperature dependence. In the ${c}^{\ensuremath{'}}$ direction only hole mobilities could be measured, which were 0.15 ${\mathrm{cm}}^{2}$/V sec at room temperature and followed a ${T}^{\ensuremath{-}2.8}$ temperature dependence. These results indicate that charge-carrier transport in durene can be treated within the frame of the band model. The charge-carrier generation process for the excitation wavelength (nitrogen laser $\ensuremath{\lambda}=3371$ \AA{}) was also studied. It is shown that the process involves a direct two-photon absorption to produce singlet excitons which then dissociate at surface states giving charge carriers. A lower limit of \ensuremath{\sim}${10}^{\ensuremath{-}48}$ ${\mathrm{cm}}^{4}$ sec/(photon molecule) was estimated for the molecular singlet-singlet excitation-rate constant.

Charge-carrier Drift Mobility in Pyrene Single Crystals

Abstract The charge-carrier drift mobility in highly pure pyrene single crystals was measured. Observed values were (3.8±0.1) ×10−3 cm2 V−1 s−1 for electrons and (3.3±0.4) ×10−3 cm2 V−1 s−1 for holes at 345 K. The mobilities increased with the temperature between 333–374 K with an activation energy of 0.43±0.01 eV for electrons.

Optical and photoelectric properties of thin layers of poly-n-epoxypropylcarbazole

The absorption of light, the luminescence, the spectral distribution of the photoconductivity and the drift mobility of charge carriers in a new organic semiconductor poly-N-epoxypropylcarbazole have been investigated.

The mobility of photo-induced carriers in disordered As2Te3and As30Te48Si12Ge10

Abstract The paper presents measurements of the drift mobility of charge carriers in radio-frequency sputtered films of As2Te3 and As30Te48Si12Ge10, as determined from the initial rate of rise of the transient photoconductivity. The data indicate that the carriers, which are concluded from subsidiary experiments to be holes, exhibit trap-limited band transport in the room-temperature region, interacting with localized levels which in both materials are situated about 0·22 eV from the Fermi level. At low temperatures, a transition occurs to a process of hopping between centres in a second set of localized states about 0·13 eV from the Fermi level, these centres again being present in both As2Te3 and As30Te48Si12Ge10. It is concluded that the greater compositional disorder of the latter material results in a change of position of the valence band mobility edge, but does not appreciably modify the localized state distribution within the mobility gap.

Structure, electrophysical properties and conductivity in polyphenylvinylenes

A study was made of the conductivity mechanism in polyphenylvinylenes in relation to molecular structure. It was found that the drift mobility of charge carriers in these polymers is in the range of 10 −5−10 −4 cm 2/V ·sec, controlled by the high concentration of fine adhesion levels ∼10 20 cm −3) and independent of the length of the macromolecular chain. It was shown that the energy spectrum of linear polyenes is determined by the length of effective conjugation. A method was developed for increasing the mobility of charge carriers.

The temperature dependence of charge carrier drift mobility in single crystals of metal‐free phthalocyanine in the β‐phase

The temperature dependence of charge carrier drift mobility in single crystals of metal‐free phthalocyanine in the β‐phase

Bond-structural approach to electrical conduction in vitreous semiconductors in the system AsSTe

Electrical resistivities of vitreous materials in the system AsSTe (composition: 12.7–43.2 at % As, 33.4–87.3 at % S and 0–41.0 at % Te) were measured in the temperature range from −70 to 120°C. The resistivity at room temperature, ranging from 10 8 to 10 17 ohm · cm, decreased with increasing tellurium content. The activation energy varied from 1.15 to 2.71 eV, and showed a similar composition dependence as in the case of resistivity. From the bond-structural approach it was suggested that the chemical bonds involving tellurium in the materials contribute to the decrease in resistivity in the order of TeTe > TeAs > TeS. The relationship between the resistivity at 25°C, ϱ 25, and activation energy, E th, was represented by the empirical formula E th = 0.1195 log ϱ 25 + 0.0899, except for a sulfur-rich material with a relatively small amount (10%) of tellurium and the materials without tellurium (the system AsS). From this formula it was derived that the pre-exponential factor ϱ 25 in ϱ = ϱ 0 exp ( E th/2 kT) was independent of composition. On the basis of the above independency, the suggestion is given that the drift mobility of charge carriers is independent of composition and that the concentration of charge carriers is the predominant factor controlling the resistivity of vitreous materials in the system AsSTe. The resistivity increased when the dispersed phase of crystalline tellurium was formed in a vitreous matrix. The amount of crystalline tellurium included in partially crystalline materials was determined from the values of the resistivity by using Maxwell's equation. This type of determination agreed fairly well with that obtained by the X-ray diffraction measurement.

Experimental Confirmation of Relation between Pulse Drift Mobility and Charge Carrier Drift Mobility in Germanium

Experimental Confirmation of Relation between Pulse Drift Mobility and Charge Carrier Drift Mobility in Germanium