Theoretical aspects of the minority carrier recombination at dislocations in semiconductors

Starting from the master equation, a diffusion equation for minority carriers in the position and energy space is first deduced. A further integration over the energy variable leads then to the definition of the recombination rate associated with any kind of defect. Applied to the particular case of dislocations, it is shown that the recombination process is made of various steps which, in first approximation occur in series: a cascade capture of the electrons and holes along the shallow dislocation states, locked by a transition between the ground states of these energy levels. We then show that for GaAs the step controlling the whole recombination process is connected with the Lax capture while for indirect gap semiconductors it should be much more controlled by the dislocation interband transitions. Self-consistent determination of the recombination is then numerically performed in the case of GaAs. We show that intrinsic EBIC contrasts may be experimentally observable and we show that this model may also be applied for the calculation of extrinsic dislocation EBIC contrasts.