Scanning Microscopy


Cathodoluminescence (CL) and Scanning Electron Acoustic Microscopy (SEAM) give complementary information on direct bandgap semiconductors when dopant impurities are introduced. CL deals with the electrical properties of the semiconductor and SEAM deals with the thermal and elastic properties and eventually with the piezoelectric properties in low doped III-V compounds. As function of the introduction of impurities for the doping of the semiconductor, the Near-Band-Edge (NBE) CL emission increases up to a maximum. and decreases when the impurities are no longer introduced in electrically active sites, but create complexes giving rise to the appearance of a Deep Level (DL) emission. The increase of the SEAM signal is related to the reduction of the thermal conductivity as function of the introduction of the impurities when the lattice contribution of the thermal conductivity is preponderant versus the electronic contribution. For highly doped III-V compounds, variation in elastic properties and presence of strain in the layers may also be evoked to explain the increase of the SEAM signal. Examples of evolution of both CL and SEAM signals are given for introduced impurities, such as, Be, C, Si in GaAs. CL and SEAM are also compared from the point of view of probed depth and spatial resolution.

Included in

Biology Commons