CATHODOLUMINESCENCE IMAGING OF N-TYPE POROUS SILICON

Cathodoluminescence (CL) from n-type porous silicon (PS) was studied u sing a transmission electron microscope (TEM) equipped with the CL det ection system. Two luminescence peaks at wavelengths of 660 nm and 420 nm were observed from a cross-sectional sample. The monochromatic CL images clearly reveal the spatial distribution of these luminescences along the depth direction; the 660 nm luminescence is mainly from near the top surface of the PS layer and the 420 nm luminescence the inter face between the PS layer and Si substrate. The increase of the 420 nm luminescence intensity upon removal of the Si substrate suggests that the excited carriers in the residual Si matrix of the PS take part in the 420 nm luminescence.