World Abstracts continued from page 63
Analytical solutions for the breakdown voltage of abrupt cylindrical and spherical junctions B. J. BALIGA and S. K. GHANDHI Solid State Electronics, 19, p.739 (1976). Analytical solutions for the breakdown voltage of abrupt cylindrical and spherical junctions have been obtained, using suitable approximations for the electric field in the depletion layer. These solutions are shown to be within _+1% of exact computer solutions for doping densities of less than I016cm-I. By normalisation to the parallel plane case, these solutions have been presented in a form which allows the computation of the breakdown voltage of both cylindrical and spherical junctions using a single curve for each situation.
A 64-stage programmable filter device has been developed. The device contains dual gate FETs for input-weighting and a 4-phase surface channel CCD register for time delay and summing. The filter output is obtained from usual floating diffusion amplifier connected to the final register stage. Fundamental delay line characteristics were measured at 10.7MHz clock frequency. A 3dB bandwidth of more than 3MHz and a differential gain of less than 5% were achieved. Using the devices, a programmable filter function has been confirmed by operating the devices as Gaussian weight filter and band pass filter.
8. Impurity bands in moderately doped semiconductors and their effect on the MOS C-V freeze-out characteristics H. D. BARBER, K. C. LEE and J. ERLE JONES Solid-State Electronics, 19, p.365 (1976). An impurity concentration and temperature dependent model of the impurity band is presented for moderately doped semiconductors. This model is then applied to explain the freezing-out MOS C.V characteristics of 1.98× 10lScm-3 p-silicon. The results show that the shape of the impurity band and its temperature dependence significantly affect the shape of the C-V curve and its temperature dependence. Fabrication and characteristics of MOS-FETs incorporating anodic aluminium oxide in the gate structure
R . K . RAYMOND and M. B. DAS So[idState Electronics, 19, p.181 (1976). Anodie aluminium oxide films have been grown by means of a simple process which is compatible with the existing planar silicon IC fabrication technology. Device structures have been fabricated and tested in order to demonstrate the usefulness of anodised layers of evaporated aluminium in a multiple layer metallisation scheme. Results of anodisation of thin aluminium layers on a silicon substrate indicate complete conversion of aluminium into aluminium oxide and in addition, formation of a thin underlying layer of silicon dioxide. For te anodic aluminium oxide a growth rate of 11.5fl,/volt at a current density of 0.5mA/em 2 has been found to produce quite satisfactory quality of insulating layers. Experimental results are presented illustrating the C-V and I-V characteristics of p-channel MOS-FETs with both the partially anodised stacked-gate structure and the overanodised double-oxide layer gate structure. Discharge of MNOS structures at elevated temperatures L. LUNDKVIST, C. SVENSSON and B. HANSSON Solid State Electronics, 19, p.221 (1976). The discharge behaviour of MNOS structures without voltage applied, is investigated at temperatures from 25 to 300~C, for times from I0 min to about lk. The observed discharge behaviour is explained by a theoretical model, including two discharge processes. The two processes are direct tunnelling from traps and thermal excitation of these traps. It is shown that static retention times of more than 10 yr at 85°C is attainable. Also, discharge with voltage applied is investigated and shown to agree with the model when the voltage is small enough.
7. Charged Coupled Devices An input-weighted CCD transversal filter T. S A K A U E , M. IWASAWA and K. MATSUSHIMA Proceedings o f the 8th Conference (1976 International) on Solid State Devices, Tokyo, 1976; Japanese Journal of Applied Physics, 16, Supplement 16-1, pp.391-396 (1977). A novel method for constructing charge-coupled device (CCD) transversal filters is presented. In the filter, transversal filtering action is implemented by introducing weighted input signals into each CCD register stage. The aim of such an input weighted CCD transversal filter was to eliminate some of the disadvantages in conventional CCD filters, i.e., the split-electrode filters or trapped delay line filters. The split electrode filter is non-programmable and requires a complex sensing circuit. The tapped delay line filter has a low transfer efficiency and requires an external summing circuit.
Application of the direct observation of nuclear reaction to the study of ion implantation
A. C A C H A R D and J. P. THOMAS Acta electronica, 19(I), p.41 (1976). (in French only.) The direct observation of the nucler reactions induced by MeV range ions allows the analysis of light elements (Z=20) at the surface of a heavy matrix (as far as a few microns in depth) with a good sensitivity (down to 1012 at.cm-2). It is shown that depth distribution can be measured with a resolution as low as 100~ in best bases. This technique allows particularly the study of low-Z ion-implanted layers in materials, and complements the elastic ion scattering technique, which is better adapted for high-Z ion analysis. Many examples are given. The effect of electron irradiation on CdS-PbTe and CdS-Te thin-film diodes
I. SPANULESCU and N. BALTATEANU Int. J. Electronics, 40(2), p.147 (1976). Some heterojunetion structures based on CdS-Te and p-type PbTe thin films were obtained by vacuum evaporation. The effect of 3MeV electron irradiation on these heterojunctions were studied. It was found that electrical characteristics of CdS-PbTe and CdS-Te thin-film diodes strongly depend on electron-irradiation doses and preparation conditions of samples. Frozen-in native defects in semiconductor compounds
K. I. H A G E M A R K J. Phys. Chem. Solids, 37, p.461 (1976). A semiconductor compound M X is discussed from a thermodynamic point of view. The concentrations of some possible native point defects have been calculated as functions of the two thermodynamic parameters temperature T, and partial pressure of M, pM. Three cases are discussed: (A) Complete equilibrium(M and Xatoms are mobile). (B) Frozen-in X atoms only. (C) Completely frozen-in M and Xatoms. In the two latter cases a two component-two phase system has three degrees of freedom, not two, as in the case of a complete equilibrium. Thus, the calculations illustrate the importance of the 'thermal history' of a crystal. On the new procedure for the determination of surface conditions in thin films with internal layer inhomogeneity W. MACIEIEWSKI and A. D U D A Solid State Communications, 20, p.65 (1976). A method for determining the surface conditions on both surfaces of the film, based in the thickness dependence of Iocalised states is proposed. A study of Pd2Si films on silicon using Anger electron spectroscopy D. J. FERTIG and G. Y. ROBINSON Solid State Electronics, 19, p.407 (1976). Auger electron spectroscopy (AES) combined with in situ sputter etching is used to quantitatively evaluate the growth kinetics of thin films of Pd2Si on (111) Si substrates. The growth of Pd2Si found to be diffusion limited and to be characterised by an activation energy of 1.4+0.2eV in close agreement with previous results obtained on thicker Pd2Si films. AES is also used to uniquely identify the silicide phase Pd2Si. Measurement of the expansion occurring during Pd2Si film formation indicates the Fd2Si film is about 20% thicker than expected. Correlation of the AES results with careful electrical measurements of the Pd2Si/Si interface reveals that the contact barrier energy ~ Bn decreases slightly with increasing thickness of the Pd2Si film. A 3% decrease in~b Bn was observed for complete conversion of 500.~, of Pd to Pd2Si.