B. Pratt

Diffusion of Lithium into Ge and Si

Lithium was diffused into Ge and Si at temperatures 300°−400°C and 400°−500°C, respectively. The diffusion was carried out in an inert gas atmosphere by decomposing LiAlH4. The concentration of Li impurities as a function of depth from the surface of the sample was determined by lapping down thin layers of the diffused part of the sample and measuring the conductance of each of these thin layers. An erfc was chosen to fit the experimentally measured concentration curve from which the diffusion constant D for each temperature of diffusion was determined. The following dependence of temperature was found: D=9.10×10−3exp(−13100/RT) for Ge, and D=2.65×10−3exp(−14500/RT) for Si, where D is measured in cm2/sec, T in °K, and R=1.98 cal/°K.The deviation in the experimental values of D was not more than ±10% for Ge and ±20% for Si.

A new method for producing narrow propagating domains of acoustic flux in piezoelectric semiconductors

Abstract A new method of producing propagating flux domains is described. The method is particularly useful for homogeneous samples of GaAs and InSb where, under normal conditions, only broad stationary flux distributions can be amplified from thermal background. The characteristics of the domains and their advantages in studies of the acoustoelectric effects are discussed.

Chemical vapor deposition of amorphous silicon prepared from SiF2 gas

A new chemical vapor deposition (CVD) method for the production of amorphous silicon films from SiF2 gas is described. About 1% (atomic) fluorine is incorporated in the film, its concentration decreasing with increasing deposition temperature. Optical, electronic, and structural properties of the films are reported.

Dependence of photoluminescence of n-GaAs on surface treatment

Abstract The changes in the intensity, shape and location of characteristic photoluminescence lines caused by various surface treatments in Te doped GaAs samples at 80 K were studied. The depth of the damage caused by such treatment is estimated. An explanation of the shifts of the characteristic lines based on the varying contribution of far donor-acceptor pairs is proposed.

Time and spatial distribution of amplified acoustic flux in n‐InSb

The growth process of amplified acoustic flux in n‐InSb under an applied constant‐current pulse is analyzed in detail, taking into account flux blocking and reflection at the contact‐semiconductor interfaces. The analysis accounts well for the observed time and spatial distribution of the amplified flux, provided spurious effects associated with current feedback and hole injection is eliminated. The measurements provide conclusive evidence that the predominant source of the amplified flux in n‐InSb is the thermal‐equilibrium phonon distribution; the piezoelectric shock produced at the contact boundaries by the onset of the applied pulse plays no role in this respect. The information derived here on the detailed mechanism governing the flux growth is utilized in measurements of the gain parameters in InSb to be described in the following paper.

Measurements of the acoustic gain parameters in n‐InSb

The drift‐velocity dependence of the acoustic gain in n‐InSb at 77°K is derived from measurements of the rate of growth of the acoustoelectric field in the sample under constant‐current pulses of different amplitudes. The amplified acoustic flux monitored by the acoustoelectric field originates from the thermal‐equilibrium phonon distribution in the crystal. Results obtained for samples of different carrier concentrations are compared with the predictions of microscopic theories applicable to InSb (ql> 1). For low drift velocities the agreement between theory and experiment is very good. For drift velocities approaching the thermal velocity, on the other hand, the experimental data deviate markedly from the theoretical predictions. In this range appreciable carrier heating takes place, an effect that has not been adequately taken into account in the existing theories. The data also provide estimates for the nonelectronic (lattice) attenuation factor and for the initial thermal flux density. The values obt...

Measurements of acoustoelectric gain and lattice attenuation in n-GaAs

Measurements of the non-ohmic behaviour associated with acoustoelectric amplification were employed to derive the frequency dependence of the small signal electronic gain parameter alpha 0 and the lattice attenuation alpha l in n-GaAs. Samples of different carrier concentrations at different temperatures were used to vary the frequency of the amplified flux. The use of a single frequency model in the derivation of alpha 0 and alpha 1 is justified in the text.

Investigation of Polarization Processes and Electric‐Field Distribution in Photoconducting Insulators

Polarization processes in partially illuminated photoconducting insulators were further investigated with a view to elucidating some discrepancies between experiment and theory. Experiments performed on single crystals of NaCl which had been colored by x‐ray irradiation only inside a well‐defined strip showed that the theory previously proposed was correct. The distribution of the electric field along the sample, at various stages of the polarization process, was recorded by means of a moving light‐probe scanning method. The results showed that the deviations from theory observed when the whole sample was colored were associated with the distortion of the electric‐field distribution outside the directly illuminated strip, as a result of extraneous carrier generation by scattered light.

Determination of the proportional contents of ingredients in InxAl1−xP, InxGa1−xP, and AlxGa1−xP by radioactive source x‐ray fluoroscopy

Curves are presented for the determination of the proportional contents of ingredients in InxAl1−xP, InxGa1−xP, and AlxGa1−xP from the relative intensity of x‐ray fluorescence of In, P, and Al in these materials. The curves apply for the case where fluorescence is induced in the ternary compounds by the 5.9‐keV x rays from an 55Fe radioactive source. Each curve has to be calibrated at one point with pure InP or AlP to normalize the system for detector efficiency and for inaccuracies in the cross sections used in the calculations. The accuracy of the results depend on x. Assuming inaccuracies of ±10% in all the coefficients used, the worst deviation in x is ±0.04 at x=0.50. Experimental verification is presented for the case of InxGa1−xP .Curves are presented for the determination of the proportional contents of ingredients in InxAl1−xP, InxGa1−xP, and AlxGa1−xP from the relative intensity of x‐ray fluorescence of In, P, and Al in these materials. The curves apply for the case where fluorescence is induced in the ternary compounds by the 5.9‐keV x rays from an 55Fe radioactive source. Each curve has to be calibrated at one point with pure InP or AlP to normalize the system for detector efficiency and for inaccuracies in the cross sections used in the calculations. The accuracy of the results depend on x. Assuming inaccuracies of ±10% in all the coefficients used, the worst deviation in x is ±0.04 at x=0.50. Experimental verification is presented for the case of InxGa1−xP .

Mode conversion and round-trip gain of ultrasonic flux in n-GaAs

Abstract Round-trip acoustoelectric gain has been observed in n -GaAs filaments oriented along the [110] axis. The special conditions required for this effect are obtained through partial conversion upon reflection of active transverse to non-active longitudinal waves. Experiments in which the relative contributions of the two reflected modes to round-trip gain is varied are described.