Response of Si and GaP p-n Junctions to a 5- to 40-keV Electron Beam

Abstract

This paper reports the use of the scanning electron beam technique for a determination of diffusion lengths in Si and GaP p‐n junctions and of the recombination cross section of dislocations in n‐type Si. This determination is based on the measurement of the current generated in reverse‐biased Si and GaP p‐n junctions by an electron beam of 5–40 keV energy. After applying corrections for backscattered and secondary emitted electrons the junction current determined experimentally is compared with calculated values using known principles of charge collection in p‐n junctions. Diffusion lengths on both sides of the depletion region enter the calculations as free parameters which are adjusted to fit the experimental data. The experiments described are directly related to the display of lattice defects previously investigated by the same technique. Si p‐n junctions: The experiments lead to a diffusion length profile in the phosphorus diffused n region which qualitatively can be understood from the concentration profile in the same region. An upper limit of the cross section for recombination at dislocations in n‐type silicon has been determined as 1.9×19⁻¹² cm². The results support the mechanism of contrast creation in the scanning electron beam display of dislocations as proposed earlier. GaP p‐n junctions: Diffusion lengths on both sides of the space‐charge region have been found to be at least in order of magnitude agreement with values determined by other experimental techniques.