Hall Effect Mobility Research Articles

Transport properties of photogenerated carriers in relaxation-case cadmium telluride films

The transport properties of photogenerated carriers in semi-insulating ($\ensuremath{\rho}={10}^{8}\ensuremath{-}{10}^{9}$ \ensuremath{\Omega} cm) polycrystalline films of CdTe are investigated. Measurements of the spectral variation of the optical-absorption coefficient and photomagnetoelectric short-circuit current are employed to obtain excess carrier diffusion lengths in films prepared at substrate temperatures of 150, 250, and 350 \ifmmode^\circ\else\textdegree\fi{}C. Analysis of the data also yields values for an effective Hall mobility, which, with stated approximations, allows an estimate of the diffusion-length lifetime ${\ensuremath{\tau}}_{0}$. Excess carrier diffusion lengths and diffusion-length lifetimes are found to be extremely small and in general agreement with earlier predictions concerning the magnitude of these parameters in relaxation semiconductors.

Measurement techniques in thin film polycrystalline materials and devices (solar cells)

A discussion of the relevance and applicability of basic bulk material and single-crystal semiconductor measurement techniques to thin film polycrystalline materials and devices is presented. The measurement techniques emphasized include resistivity and the Hall effect. Basic parametric relations for resistivity and the Hall effect coefficient are presented together with a discussion of the modifications due to film thickness, grain size, grain boundary conductivity and the presence of a substrate. The use of other electronic measurement techniques ( e.g. surface photovoltage, photoconductivity and capacitance-voltage methods) is reviewed. Automated materials characterization and analysis methods such as scanning electron microscopy, secondary ion mass spectrometry, Auger electron spectroscopy and X-ray crystallography are presented in their dual role of providing fundamental materials parameter values and of verifying results determined by other electronic methods. The technical literature is surveyed to determine the most widely applied thin film resistivity and Hall effect (mobility) analytical and experimental measurement methods. Widely used measurement techniques for other relevant parameters ( e.g. minority carrier lifetime, diffusion length etc.) are also identified, and an estimate of their efficacy in yielding results ( i.e. parameter values) for thin films consistent with overall device performance is made. The measurement approaches producing the most viable performance indicators are then analyzed for needed improvements, greater measurement reproducibility etc.

Thermoelectric and galvanomagnetic properties of systems with mutually penetrating components

The effective coefficients of thermal conductivity, electrical conductivity, thermal emf, the effective Hall mobility, and the effective Hall coefficient are determined. The analytical dependences obtained are compared with experimental results for a Bi-Cd alloy.

Hall and field effect mobility of CdS films sublimed on sapphire substrates

A method of producing thin films of cadmium sulphide by closed spaced sublimation of single crystal CdS on sapphire substrates is described. The deposited films are polycrystalline with grain sizes ranging from 4 to 8 μm. The Hall mobility of these films is comparable to that of the parent crystal and is controlled by intercrystalline barrier scattering. At low values of the surface potential the field effect mobility increases with the surface potential due to the decrease in the intercrystalline barrier height. At large values of surface potential the mobility decreases due to surface scattering. The field effect mobility, determined from the measurement of the transconductance of field effect transistors, however, is considerably lower than the Hall mobility. There is enough evidence showing that these low values of the field effect mobility do not indicate any degradation in the quality of the film interior but are caused by the presence of traps at the semiconductor-insulator interface.

Hall Effect Measurements of Zn Implanted GaAs

The isochronal annealing behavior of the effective surface carrier concentration and effective Hall mobility of Zn-implanted layers in GaAs has been investigated. Ion implantation has been performed with 60 keV Zn ion at various doses up to 1016/cm2 at room temperature and 400°C. An annealing stage for effective Hall mobility exsists between 600 and 700°C. After annealing at 700°C and above, ionized-impurity scattering is a dominant mechanism affecting the mobility. The highest mobility obtained is 170 cm2/V sec. The maximum effective surface carrier concentration is achieved after annealing at temperatures around 700°C. Samples implanted with doses up to 1015/cm2 show a 100% doping efficiency and those implanted with heavier doses show a saturation tendency in the effective surface carrier concentration.

The Properties of Thin Epitaxial PbTe Films Prepared Under Very Clean and Closely Monitored Conditions

With the now available evidence that the structural and electrical properties of semiconductor films are a strong function of the conditions of preparation it has become apparent that if high mobility material films with reproducibly good electrical properties are to be realised, then preparation must be in very clean and closely monitored conditions with a tight control on important parameters. As an illustrative experiment 500Å thick lead telluride films have been grown on mica under clean substrate, clean source and clean environment conditions. SIMS surface analysis techniques were used to check the contamination state of the substrate and subsequent monitoring of the film nucleation and structure showed that a close control of film crystallography was possible. After growth the films were annealed until their electrical properties stabilised. In situ electrical measurements showed the annealed films to have near intrinsic carrier concentrations and bulk like Hall and field effect mobilities (∼500 cm2V-1sec-1) and these properties were reproducible.

Influence of substrate temperature on basic electrical properties of CdSe thin films

The influence of substrate temperature in the range 25°–200°C on the basic electrical properties of CdSe thin films has been studied and a comparison with the results of other authors and with the electrical properties of CdSe thin films annealed in oxygen and selenium vapours has been made. It is shown that in the temperature range in which the grain size of the film does not change with the substrate temperature, the film resistivity increases with increasing substrate temperature while the carrier concentration decreases monotonically; the effective Hall mobility has a more complicated dependence, exhibiting a maximum at a temperature of about 40°C. By analysing the carrier excitation mechanism it is proposed that in the films studied three donor excitation levels exist, the first one ( ΔE=0.025 eV) corresponding to the impurity atoms, and the second ( ΔE=0.14 eV) and third ( ΔE=0.4 eV) to the divalent selenium vacancies. The donors are assumed to be compensated by some acceptor centres. The model allows the great variety in n m=f(1/ T) curves to be explained and gives useful information about the carrier excitation mechanism involved.

The influence of O 2 and N 2 on the hall and field effect mobilities in CdSe and PbTe thin films

Thin films of CdSe and PbTe were evaporated onto SiO in a vacuum system in which a pressure of less than 5 × 10 −10 torr was available. The Hall and field effect measurements were made directly after producing the sample. Furthermore, these measurements were repeated under various partial pressures of O 2 and N 2 up to nearly 10 +2 torr. A remarkable influence of these gases on the mobilities was observed. One can understand this effect by considering that p-type regions are formed at the surface of the n-type semiconductors and thus a diminution of the measured mobilities occurs.

Hall Effect of an Inhomogeneous Material

The effective Hall mobility is calculated for a material containing inclusions which have a conductivity and Hall mobility differing from those of the matrix in order to investigate whether Hall-effect-Seebeck-effect anomalies can be explained by the presence of inclusions. The calculation is performed analytically using a method by which Airapetiants has determined the effect of inclusions on the Seebeck effect, and numerically by solution of the Laplace equation with the relaxation method. The effective Hall mobility is largely dependent on the ratio of the specific conductivity of the inclusion to that of the matrix. The possibility of obtaining a sign reversal of the Hall effect when the Hall effects of matrix and inclusion have opposite sign is largest when the respective conductivities are about equal. The Hall effect anomaly occurring in Li-doped NiO at 600 °K might be explained by assuming that 1% inclusions having a negative Hall effect with a Hall mobility of ≈ 5 cm2/V sec are present. However, this explanation requires the specific conductivity of the inclusions to be proportional to the Li concentration which seems improbable. It is shown to be impossible to explain the Hall-effect-Seebeck-effect anomaly of chalcogenide glasses with the present model.

THE FILMS ON T. G. S. CLEAVED IN U. H. V.

The surface of T. G. S. is observed by measuring the resistance, the Hall effect mobility, and the field effect mobility of an evaporated semiconducting electrode. On the normaly preparated T. G. S. surface the field effect mobility is up to twenty times smaller than the Hall mobility, on in U. H. V.-cleaved T. G. S. (pressure less than 5 x 10-9 torr) against that the two mobilities are praktically equal. This different behaviour is a consequence of the ion absence at the U. H. V.-cleaved T. G. S. surface.

Mechanical and electrical properties of epitaxial silicon films on spinel

Silicon films on single crystal magnesium-aluminium spinel slices and similarly on sapphire are strained under compressive stress. This is due to the difference in thermal expansion and to the high growth temperature, causing a curvature of the slices. The coefficients of thermal expansion have been measured by a dilatometer. From the curvature measured by a stylus tracing method a residual stress of about 8 × 10 3 kp/cm 2 has been determined. The expected change in resistivity, effective Hall mobility, and band gap has been calculated from the known influence of stress on the electrical properties of bulk semiconductors, and has been compared with the experiments. The measured mobility as a function of carrier concentration has a maximum between 10 16 and 10 17 carriers per cm 3. The highest mobilities measured were 600 cm 2/V-sec for n-type and 350 cm 2/V-sec for p-type silicon films. The observed decrease of carrier mobility with decreasing carrier concentration (for n, p ≤ 10 16 cm −3) and the relatively low minority carrier lifetime are explained by the assumption of space-charges localized at crystal defect accumulations. In accordance with this assumption an anomalous dependence of mobility on temperature has also been found. The existence of localized space charge regions was further confirmed by the change of photo-voltage on scanning the film with a finely focused laser beam. First characteristics of MOST's on relatively thick silicon films on spinel do not show any remarkable difference from that of transistors on bulk silicon, both having been produced by applying the usual MOS technology.

Field-effect studies on indium antimonide films

Field effect studies have been carried out on thin film InSb inert insulator solid-solid interfaces. The films were prepared by the protected recrystallization method, namely vacuum evaporation and subsequent annealing of the resulting insulator-semiconductor-insulator sandwiches. The high annealing temperatures permissible without danger of reevaporation of the more volatile component gave films with high mobility of approximately 103−104cm2/V-s and relatively low carrier concentrations of approximately 1016−1017/cm3. The good bonding of the insulator on to an inherently clean semiconductor surface resulted in a low fast surface state density of approximately 5 × 1011/cm2, which would permit the use of these films for field effect transistor applications. Thin films are very well suited for field effect investigations. Surface Hall effect and surface conductivity against surface potential gave the trapped and mobile charge density with the relevant Hall and field effect mobility directly. A model of fast surface states based on these results is proposed.

Surface mobility of holes in thermally oxidized silicon measured by the field effect and the hall effect

A comparison of the surface Hall and field effect mobilities indicates few, if any, surface states within ·13V of the valence band. By combining changes in the field plate voltage and a bias voltage between the surface layer and the bulk crystal, it is possible to vary independently the total number of charges in the surface channel and the effective thickness of the channel. The dependence of the surface mobility upon these parameters can be explained by a combination of enhanced lattice scattering and screened charged impurity scattering at the surface. A possible surface quantization effect is described.

379. Variation of field effect mobility and Hall effect mobility with the thickness of the deposited films of tellurium: S. K. Ghosh, J. Phys. Chem. Solids, 19 (1/2), April 1961, 61

379. Variation of field effect mobility and Hall effect mobility with the thickness of the deposited films of tellurium: S. K. Ghosh, J. Phys. Chem. Solids, 19 (1/2), April 1961, 61

Variation of field effect mobility and Hall effect mobility with the thickness of the deposited films of tellurium

Experimental results of the variation of conductivity. Hall mobility and field effect mobility with the thickness of the evaporated films of tellurium is reported. A tentative explanation of the experimental results is offered. The low values of Hall mobility are explained to be mainly due to the scattering of the carriers at the intercrystalline boundaries