Low temperature semi-quantitative analysis of local electrical field in silicon diode by transmission electron microscopy

Laboratoire de Physique du Solide, ESPCI – UPR5 CNRS, 10 rue Vauquelin, 75231 Paris Cedex 05, France

Corresponding author: cecil.cabanel@espci.fr

Received: 5 October 2004
Revised: 17 January 2006
Accepted: 23 January 2006
Published online: 18 May 2006

Abstract

The local electric behaviour of IMPATT diodes was studied by scanning transmission electron beam induced current in cross-section method (X-STEBIC). This technique of induced current measurement makes it possible to probe the depletion zone of a junction with the beam of a transmission electron microscope. Two series of experiments were carried out. The X-STEBIC signal was analyzed according to the sample thickness and under different electrical polarizations. Moreover, these measurements were done and compared at room and low temperature (≅110 K). From these data, simulations of X-STEBIC profile allowed us to determine the main physical parameters brought into play in the signal formation. We have shown that, in the vicinity of the junction, the intensity of the induced current partly depends on the avalanche effect. The kinetic energy of the minority carriers generated by the electron beam is sufficient to induce collisions in cascade, even when the junction is not polarized. At low temperature, surface recombination has an essential role on the lateral resolution of the X-STEBIC method. By choosing carefully the range of sample thickness and by positioning the probe in the field of the diode, it is possible to optimize the resolution. Surface recombination annihilates the diffusion of the carriers so that the STEBIC image becomes a true image of the electric field. Consequently, semi-quantitative physical data can be obtained on the junction field.