Transmission electron microscopy of wide band-gap semiconductor layers

Transmission electron microscopy (TEM) is a useful method to characterise wide bandgap semiconducting layers. Different modes of TEM can be used to identify the different crystalline grains, reaction products of solid phase reactions and defects in heteroepitaxial layers. Above features are demonstrated via the example of SiC epitaxial layers, contacts to SiC and GaN layers grown on sapphire. The achieved results are the following: a) hexagonal SiC can be grown homoepitaxially by CVD (Chemical Vapour Deposition), when the C/Si ratio is kept at a low value. Cubic SiC may be nucleated on exceptionally long terraces on the surface, but even those ones are overgrown laterally, when the C/Si ratio is kept at the appropriate value. b) Ni proved to be reactive on SiC and phase identification showed Ni,Si grains with high number of voids. Therefore deposition of Ni/Si multilayers is suggested and prepared in order to get a Ni2Si layer without voids and excess carbon. c) Inversion domains in GaN layers are found to be responsible for V-shaped pits on the surface.