theoretical studies of minority carrier concentration profile and cathodoluminescence intensity in thin-凯发网

in this paper, the effects are examined of the upper and the lower sulface recombinationv elocities, si,s z, the diffusion length of excess minority carriers, l, and the thickness of the sample, h. on the minority carrier concentration profile (mccpa) nd on the intensity of cathodoluminescence (cl) from thin foils. a systematic theoretical investigation of these effects is essential lo the understanding of experimental resuits which have recently been obtained by high-resolution cl imaging studies. by solving the reduced one-dimensional steady-stale diffusion equation under the non-trivial and realistic boundary conditions that the recombination velocities si and sp on the upper and lower surfaces are allowed lo vary independently of each other, exact and anaiyiical expressions for the mccp and cl intensity (cu) are oblained for the general case of sulface recombination (sr). a number of special sr cases are discussed. the important question of the thickness dependence of the cl is addressed. conditions for linear, square or cubic dependence of cu on h are deduced together with expressions for a thickness which we call the cut-off thickness. the capability of using the present analytical resun for mccp to treat the electronbeam- induced current problem here is pointed out in passing together wlh tem or stem charge collection imaging and contrast problems of dislocations or defects. specific numerical calculations are used to display the theoretical resuits quanlilalively and reveal a variety of properties of the model controlled by different values of the parameters contained within it. the resuits obtained can be used to explain and examine the features of cl in thin-film materials when examined in tem or stem modes. in some given cases, experimental determinations of the parameters can be made: