The fundamental concept of the relaxation semiconductor proposed by van Roosbroeck and Casey is critically discussed and a new model is proposed. It is indicated that the essential behavior of carriers in this type of semiconductors can not be correctly predicted by the approximation pn_??_ni2, but can be visualized only by considering even a small deviation from pn=ni2, as derived by the present new approach. It is revealed that the injection of minority carriers can lead to a depletion of majority carriers, only when the density of filled recombination centers lies in the limited narrow region and the injection level is relatively low. This model is applicable to all cases for the minority carrier injection, whether the relaxation times of electrons and holes are large or small, and whether the density of traps is large or small.
A method is presented for quantitative PIXE analysis of thick samples of light element matrix containing a relatively small amount of heavier element. A small program for on-line personal computer has been developed for the analysis of spectra. After stripping background components from a data spectrum, an ideal Gaussian is generated for a given matrix with unit content of the element from the thick target X-ray yield Q per proton. The Q was calculated by an off-line large computer and stored in a disc as data-base of the small program. The concentrations of the elements contained are determined by fitting the Gaussian to the data spectrum. The yields Q were calculated for Ka1 Ka2 and Kβ X-rays induced by 2 MeV protons from ceramic law materials-MgO, Si3N4, SiC and Al2O3. The application to the analysis of SiC indicated the efficiency of this technique in thick target PIXE analysis.