Papers by Keyword: Electron Beam Induced Current (EBIC)

Abstract: We investigated the spatial variation of energy band structure in a SrTiO₃ (001) bicrystal with the (100) 10° tilt boundary before and after the annealing process at 973 K under a vacuum of ~10^-7 Torr and after the subsequent forming process with electrical dielectric breakdown, using electron beam induced current (EBIC) method in the temperature range between 200 and 300K. Although the EBIC contrast at the tilt boundary was weak before and after the annealing, it became visible after the forming process and stronger as the observation temperature decreased to less than 260 K. It was found that the EBIC direction at the tilt boundary is opposite to that in the matrix, i.e. the single crystalline regions of both sides of the tilt boundary. In the matrix, the EBIC increased after the annealing and decreased again after the forming process. We propose energy band structures of the bicrystalline SrTiO₃ after the annealing and after the forming process.

Abstract: Electron beam induced current (EBIC) observations have been carried out to investigate the influence of mechanical polishing (MP) direction on the dislocations formation at the Si-face c(0001) of 4H-SiC epitaxial layers. Two opposite MP directions (defined by polish pad moving direction) have been compared, which are [11-20] off-cut directions along step-up and step-down, respectively. It has been found that high density of dislocations have been formed along the polish paths for the 8o off samples with polishing pad moved in step-up direction. By contrast, step-down polishing samples have shown no significant dislocation increase although shallow polish scratches were observed. Similar experiments have also been carried out for 4o off samples, showing step-up MPs introduced more dislocations than step-down ones. The results are discussed in terms of forces along the slip plane [11-20](0001) effectively exerted by the abrasive particles on the steps.

Abstract: Electron beam induced current (EBIC) and etch pit method have been used to study the dissociation behavior of basal plane dislocations (BPDs) in 4H-SiC under electron beam irradiation. When 20 kV scanning electron beam was applied for 1 h, it has been found that BPDs whose dislocation lines were along [11-20] off-cut direction dissociated into partial dislocations (PDs) forming a stacking fault (SF) between them; while no dissociation was found for BPDs extending along other directions. These results are discussed in terms of different formation energy of SFs expanding from a pure screw type and a mixed type BPD. In addition, the angle between dislocation line of a BPD and the [11-20] off-cut direction might also play a role in determining the minimum energy for SF formation.

Abstract: Dislocations in highly doped n-type 4H-SiC (n+-SiC, n>1019 cm-3) substrate have been studied by means of electron beam induced current (EBIC). Ni/n-SiC/n+-SiC/Al structure was fabricated in order to simultaneously observe the dislocations in n-SiC epilayer and n+-SiC substrate. We have found that dark dots in the EBIC image correspond to threading screw dislocations (TSDs) and threading edge dislocations (TEDs) with the former being relatively darker. Short dark lines along off-cut are attributed to basal plane dislocations (BPDs) in the epilayer; and the randomly oriented long dark lines are caused by the BPDs in the substrate. The classification of the dislocations by EBIC has been examined by wet etching in KOH+Na2O2.

Abstract: The effect of various types of in-grown stacking faults and threading screw/edge type dislocations on carrier lifetime and diffusion lengths in 4H-SiC epitaxial films was investigated through cathodoluminescence decays and charge collection efficiencies of electron beam induced current signals at specific defects sites. Most stacking faults yielded ~40% reduction in the carrier lifetime. Moreover, drastic lifetime reductions were observed in regions containing surface triangular defects and bulk 3C polytype inclusions. Dislocations of both types serve as efficient recombination centers, though stronger reduction in diffusion lengths was observed in the vicinity of screw type dislocations.

Abstract: Cold-wall vapor phase epitaxy was utilized to grow uniform 4H-SiC layers with abrupt doping interfaces on 4o off-axis substrates. Concentrations of Al were reduced roughly 200x after 0.1 μm of epitaxy after trimethylaluminum flow was stopped. Thickness uniformity of cold-wall epitaxy across 3” wafers was as good as 3.2%. Minority carrier diffusion lengths of 27 μm-thick 4H-SiC epitaxy grown in a cold-wall design were as high as 58 μm.