Tomographic detection of micro-defects in semi-conductions due to light scattering and photoluminescence imaging

点击翻译按钮获取中文摘要

Since the defect density in ordinary semiconductor crystals is fairly low, determination of the surveillance volume is very important to get correct information about defects in the crystals. Here the volume is defined as that to be searched by a single surveillance trial and should be equal to or a little larger than the reciprocal density of the defects.The following two-step investigation resulted in successful and novel use of an ordinary IR light scattering tomography (LST) instrument for this purpose. (1) The surveillance thickness of photoluminescence (PL) due to carriers optically injected by a laser beam for LST is usually much larger than that of the laser beam diameter for LST, because the carriers diffuse out emitting PL from the position illuminated by the beam. Thus PL mapping is very effective to search for low density defects in the crystals since the defects act as usually PL killer centers and, sometimes, recombination centers. (2) The intensity modulated positions in the PL mapping were carefully surveyed by layer-by-layer tomography using a finely focused laser beam.By complimentary combination of the above two methods the defects will be clearly observed.