Hopping conductance in electron irradiated n-type GaAs

A.c. conductivity is studied in n-type electron irradiated GaAs at helium temperatures. For T < 25 K variable range hopping $\text{[σ∝exp(-b/T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)]}$ is observed. The experimentally observed low values of $\text{b(K}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}\text{)}$ are discussed. At T > 30 K the conductivity exhibits an activation energy of 0.5 meV which is attributed to excitation into an upper band. The frequency dependence of hopping conductance is σ ∝ ω^S with S=1.8 and S=0.9 depending on the degree of radiation induced damage.     

Temperature dependence of the energy separation between Γ and L minima in n-type GaSb

Energy separation ΔE_c between Λ and L minima of GaSb conduction band is deduced from temperature dependence of tunneling current in p−n junctions. ΔE_c is found to inceasing vx. temperature with a coefficient d(ΔE_c/dT) of about - 2.10^-4eV/dgK.     

Electrical properties of n-type Si layers doped with proton bombardment induced shallow donors

Sheet Hall coefficients and resistivities of n-type Si layers doped with shallow donors produced by proton bombardment have been measured between 35 and 300°K. The donor ionization energy is (26 ± 1) meV. The donor concentration profile has been determined.     

Spin-dependent photoconductivity in n-type and p-type amorphous silicon

It is found that, as in crystalline silicon, the photoconductivity in amorphous silicon prepared by glow discharge is strongly spin-dependent. In this material, the position of the Fermi level can be smoothly varied by phosphorous or boron doping and the magnitude of the spin-dependent recombination has been measured as a function of the doping: it is found to have a large maximum when the material is intrinsic. The similarities with the spin-dependent effects in crystalline and dislocation silicon suggest that the recombination process in amorphous silicon is the same as in the crystalline material and that dislocation-like centres are responsible for the spin-dependent recombination properties in both materials.     

Dependence of surface recombination velocity of p-type InSb on temperature and alpha particle bombardment

The temperature dependence of surface recombination velocity S of p-type InSb upon alpha particle bombardment is studied from photomagnetoelectric measurements between 16 and 80 K. Warming the specimen above 16 K we observe an increase of S followed by an abrupt fall of S at about 30–40 K. Further warming produces a strong maximum of S at about 100–120 K. Bombardment with alpha particles increases S at all temperatures up to about 120 K. The whole behavior is explained on the basis of a model proposed by the authors in an earlier paper.     

Hall effect in n-type GaS

Hall effect measurements have been performed for the first time on n-type GaS single crystals, grown buy the Bridgam-Stockbarger method. Electrical properties are dominated by a donor centre at 0.52 eV, with a concentration of 2.3 × 10¹⁶cm^–3. The conduction band density-of-states effective mass has been estimated to be 1.3m_e.The low temperature conduction is compatible with a hopping process with an activation energy of 0.15 eV.     

Transport parameters of n-type GaSb

The conduction band parameters of GaSb have been investigated in the temperature region 70–280 K. Hall and magnetoresistance data have been analysed according to the two band model to obtain information about the energy separation ΔE₁₂ of the conduction band minima and its temperature coefficient α₂.     

Temperature dependence of electron mobility in GaAs/GaAlAs modulation doped quantum wells

We report the temperature dependence of the drift mobility in GaAsGa_1−x Al_x As modulation doped quantum wells. A theoretical model is formulated which includes scattering by (i) residual impurities located in the well, in the barrier, and at the “inverted” interface, (ii) Si donors and (iii) accoustic phonons. Contributions from the diffused profile of doped Si impurities and the background impurities piled up at the interface, are separated through S.I.M.S. experiments and temperature dependence of the scattering rate. The density of interface scattering centers increases with alloy composition x.     

Free carrier absorption in n-type CdTe

Experimental results for free carrier absorption at room temperature in lightly doped samples of n-type CdTe, including the λ³ dependence of the absorption coefficient on the photon wavelength, can be satisfactorily accounted for in terms of polar optical mode scattering with a very small contribution by impurity scattering. Use is made of the quantum theory of free carrier absorption initially developed for direct gap III–V semiconducting compounds, which utilizes the Kane band structure and includes nonparabolicity, arbitrary spin-orbit splitting values, overlap wave function factors, and intermediate states in other bands.     

Subthreshold behavior of AlInSb/InSb high electron mobility transistors

We propose a scaling theory for single gate Al In Sb/In Sb high electron mobility transistors(HEMTs) by solving the two-dimensional(2D) Poisson equation. In our model, the effective conductive path effect(ECPE) is taken into account to overcome the problems arising from the device scaling. The potential in the effective conducting path is developed and a simple scaling equation is derived. This equation is solved to obtain the minimum channel potential Φdeff,minand the new scaling factor α to model the subthreshold behavior of the HEMTs. The developed model minimizes the leakage current and improves the subthreshold swing degradation of the HEMTs. The results of the analytical model are verified by numerical simulation with a Sentaurus TCAD device simulator.     

Electrical properties of n-type GaS single crystals

Hall effect and Thermally Stimulated Currents (TSC) measurements have been carried out with the current flowing perpendicular to the c-axis on n-GaS crystals grown both from the melt by the Bridgman-Stockbarger method and from the vapour by chemical transport with iodine. An impurity hopping conduction with an activation energy of 0.2 eV has been evidenced in the range of temperatures between 200 and 300 K. The results of TSC measurements indicate the iodine as being responsible for a donor level at 0.44 eV from the conduction band.     

An infra-red study of defects produced in n-type silicon by electron irradiation at low temperatures

The infra-red local mode absorption produced by irradiation of n-type silicon by 2 MeV electrons at temperatures in the range 100–140°K has been investigated. A new band at 884 cm^-1 has been observed and interpreted as due to a vacancy— oxygen complex (A-centre) with a trapped electron.     

Electrical properties of n-type vapor-grown gallium nitride

Hall measurements are reported for undoped and Zn-doped vapor-grown single crystal GaN on (0001) Al₂O₃ layers with 298 K carrier concentrations (n-type) between 1·4×10¹⁷cm^?3 and 9×10¹⁹ cm^?3. Then n～10¹⁷ cm^?3 crystals (undoped) have mobilities up to μ～440 cm²/V sec at 298 K. Their conduction behavior can be described by a two-donor model between 150 and 1225 K and by impurity band transport below 150 K. Crystals with n≥8×10¹⁸ cm^?3 show metallic conduction with no appreciable variation in n or μ between 10 and 298 K.Results of mass spectrographic analyses indicate that the total level of impurities detected is too low to account for the observed electron concentration at the n～10¹⁹ cm^?3 level, and suggest the presence of a high concentration of native donors in these crystals. No significant reduction in carrier concentration was achieved with Zn doping up to concentrations of ～10²⁰ cm^?3 under the growth conditions of the present work, and no evidence was found to indicate that high conductivity p-type behavior may be achieved in GaN. The influence of factors such as growth rate, crystalline perfection and vapor phase composition during growth on the properties of the layers is described.     

Temperature dependence of compositional changes of SiO2 surface during ion and electron bombardment

The influence of ion (Ar⁺ 0.5 keV, 2 microA/cm²) and electron (2 keV, 2 mA/cm²) bombardment on the elemental composition of SiO₂ was investigated in the temperature range of 270–790 K. Elemental composition was controlled by AES. It was found that both ion and electron bombardment resulted in an increasing amount of Si₉₂ (elemental silicon) and in decreasing amounts of both O₅₁₀ and Si₇₈ (silicon bound to oxygen). The temperature influence on the composition of SiO₂ is negligible under ion bombardment while the amount of Si₉₂ strongly increases under electron bombardment at temperatures exceeding 600 K. The mechanism of temperature dependence is discussed.     

Field dependence of hole mobility in TPD-doped polystyrene

Field and temperature dependence of hole mobility in N,N^′-diphenyl-N,N^′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) doped in polystyrene (PS) is studied using the transient photoconductivity technique. We observe both the positive and negative field dependence of mobility with increasing field and temperature. The field and temperature at which negative field dependence begins is low compared with earlier reports on similar systems (with 20 wt% dopant concentration). Results are discussed on the basis of the Gaussian disorder model (GDM), which predicts that the interplay of both the energetic and positional disorder of dopant molecules in the sample decides the slope of the logμ versus E^1/2 plot. The observed mobility dependence is rationalized on the basis of low energetic disorder in the sample. The reason for low energetic disorder is purely due to the film morphology of the sample. Even for a dopant concentration of 20 wt%, we observe clustering and chaining of TPD molecules, which may provide low energetic and positional disorder.     

Irradiation-induced compensation of n-type germanium — electrical measurements

The temperature dependence of the Hall effect in an n-type germanium sample following each of a series of 2 MeV electron irradiations at 80 K has been analysed. It is shown that conversion to p-type proceeds by the introduction of defects which are acceptors contrary to the suggestion made recently that conversion proceeds by the removal of donors.     

Quantum efficiency and radiative lifetime in degenerate n-type GaAs

The hole lifetime, the radiative lifetime, the non-radiative lifetime, and the internal quantum efficiency in degenerate n-type GaAs crystals have been investigated with a simplified model of degenerate semiconductors, in which the recombination constant B is approximately proportional to the$\text{?13}\text{8}$ power of the electron density.In n-type GaAs at 77 K, the radiative lifetime reaches a minimum equal to 4 × 10^?9 sec. at 6 × 10¹⁷ cm^?3, and the internal quantum efficiency exhibits a maximum equal to 50% at 8 × 10¹⁷cm^?3, in good agreement with the theoretical prediction of Dumke and the experiments of Cusano. At high impurity concentrations, the polytropy effect is taken into account in the case of GaAs crystals doped with tellurium and selenium. Finally, it is suggested that, for a given high concentration, the internal quantum efficiency increases with increasing temperature, in accordance with the observed results.     

Multiphoton electronic-spin generation and transmission spectroscopy in n-type GaAs

Multiphoton electronic-spin generation in semiconductors was investigated using differential transmission spectroscopy. The generation of the electronic spins in the semiconductor samples were achieved by multiphoton pumping with circularly polarized light beam and was probed by the spin-resolved transmission of the samples. The electronic spin-polarization of conduction band was estimated and was found to depend on the delay of the probe beam, temperature as well as on the multiphoton pumping energy. The temperature dependence showed a decrease of the spin-polarization with increasing temperature. The electronic spin-polarization was found to depolarize rapidly for multiphoton pumping energy larger than the energy gap of the split-off band to the conduction band. The results were compared with those obtained in one-photon pumping, which shows that an enhancement of the electronic spin-polarization was achieved in multiphoton pumping. The findings resulting from this investigation might have potential applications in opto-spintronics, where the generation of highly polarized electronic spins is required.     

Photoelectronic characterization of n-type silicon wafers using photocarrier radiometry

Photocarrier radiometry (PCR) was used to characterize four n-type silicon wafers with different resistivity values in the 1-20 Ω cm range. Simulations of the PCR signal have been performed to study the influence of the recombination lifetime and front surface recombination velocity on them; besides, the transport parameters (carrier recombination lifetime, diffusion coefficient, and frontal surface recombination) of the wafers were obtained by means of a fitting procedure. The PCR images that are related to the lifetime are presented, and the first photoelectronic images of a porous silicon sample are obtained.     

InSb霍尔传感器输出电压温度特性的研究

对InSb霍尔元件在－135～65℃内的霍尔电压的温度特性进行了测量,研究在恒流源和恒压源条件下其输出电压随温度的变化情况,并对其工作温度、线性范围及应用进行了探讨。