THE STRUCTURE OF POROUS GALLIUM-PHOSPHIDE

Free films of porous GaP have been obtained for the first time and the ir microstructure has been investigated by transmission electron micro scopy (TEM) and Raman scattering (RS). The TEM results showed that the microstructure of the porous-Gap films has a complicated spatial stru cture, but the local crystallographic orientation is preserved and cor responds to the initial substrate. Narrowing of the half-width and a s imultaneous low-frequency shift of the LO-phonon peak were observed in the RS spectrum. This behavior can be satisfactorily explained in ter ms of the change in the plasmon-phonon interaction as a result of a de crease in the carrier density. A shift in the frequency of surface pho nons of porous GaP as a function of the local void formation condition s was also observed. It is shown that in principle porous layers can b e obtained without the void surfaces being covered appreciably with ox ides or other products of an electrochemical reaction. (C) 1998 Americ an Institute of Physics.