INFLUENCE OF SURFACE STATES ON THE ELECTRIC FIELD OF THE N-P JUNCTION

Abstract

The structure and properties of semiconductor devices largely depend on the distribution of the internal
electric field, which is created by the distribution of ionized impurities. One of the methods for the controlled
introduction of donors and acceptors is their diffusion into the bulk of the semiconductor. The existence
of surface electronic states in the band of forbidden energies has an uncontrollable effect on the distribution
of the electric field in the surface region. The purpose of the study is to analyze the influence of surface
states on the distribution of the electric field in a diffusion n-p junction. Research objectives. 1 – Develop an
algorithm for the numerical solution of the Poisson equation, taking into account the general electrical neutrality
of the n-p junction and the density of surface states in the emitter. 2 – Calculate numerically the distributions
of electric potential, electric field strength, electron and hole concentrations in a diffusion n-p junction.
3 – Analyze the influence of surface states on the change in the internal electric field and the rate of
surface recombination of nonequilibrium charge carriers. As a result, the influence of surface states on the electric field distribution in a diffusion n-p junction in silicon was numerically simulated. The model is based
on a numerical solution of the Poisson equation with boundary conditions that include the condition of the
overall electrical neutrality of the sample. It is shown that the density of electronic states on the emitter surface
creates a narrow range of electric charge density distribution. The maximum value of the modulus of the
electric field strength in this region exceeds the similar value in the n-p junction by three times or more. The
electric field strength caused by the surface charge directs minority charge carriers towards the surface. This
increases the effective rate of their recombination. Reducing the surface charge density or changing its sign
is one of the tasks of semiconductor device technology.