GROWING HELICAL DENSITY WAVES IN SEMICONDUCTOR PLASMA,
Abstract
A theoretical and experimental study is made of growing screw-shaped waves of electron-hole densityiently large parallel electric and magnetic fields. The formulation of a physical model for the growth mechanism and motion of this helical wave leads to several interesting results. The wave may exhibit growth in two distinctly different forms. For unequal densities of positive and negative carriers, the growth is spatial, corresponding to unidirectional traveling-wave amplification. For equal or nearly equal carrier densities, the growth may be temporal, leading to instability. The latter case corresponds to the helical instability proposed by others as an explanation of the anomalous diffusion in a gas discharge with a longitudinal magnetic field, and of the oscillistor effect in semiconductors. It is shown further that growing helical waves may be obtained in a particularly simple physical configuration. All that is required is a uniform semiconductor bar with a low recombination surface, ohmic contacts, and moderate applied electric and magnetic fields. A detailed and quantitative mathematical description of the growth and propagation characteristics of the waves is presented. Experimentally, the growing helical waves were excited and observed in bars of 30 ohm-cm germanium at and above room temperature. The growth and phase characteristics of the waves were found to be in excellent agreement with the theoretical predictions. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 17, 1963
- Accession Number
- AD0432393
Entities
People
- C. E. Hurwitz
Organizations
- Massachusetts Institute of Technology