Crystallinity of p-type porous silicon and its change with heat-treatment

The crystallinity of p-type porous silicon has been investigated with X-ray diffraction (XRD), thermal analysis, and transmission electron microscopy (TEM). Each XRD peak is composed of a sharp Bragg reflection peak and a dif fuse diffraction. The diffuse diffraction is not related to the presence of amorphous phase judging from the thermal analysis and the comparison with the XRD of amorphous silicon. The shape of the XRD pattern changes with hea t-treatment at temperature as low as 400 degrees C. The TEM observation als o reveals the enhancement of crystallinity by the heat-treatment. The resul ts imply that no amorphous phase is formed in porous silicon with high resi stivity.