Appearance of local strain fields and high electrical conductivity of macro-defects in P+-implanted 4H-SiC

K Ishiji,Y Hirai,S Kawado,S Nagamachi

doi:10.1063/1.4807158

Abstract

We investigated the implantation-temperature-dependence of defect structures of P+-implanted 4H-SiC using synchrotron white-beam x-ray topography, which revealed hitherto unknown defect images in SiC implanted at 300 and 500 °C, though they were not observed in SiC implanted at 30 and 150 °C. These defects corresponded to small bump and saucer-pit defects, called generally “macro-defects,” which were originally located on the initial surface of the SiC epilayer. After subsequent annealing at 1600 °C, the x-ray topographic images of the bump defects were similar to those of threading screw dislocations, but the images of the saucer-pit defects were not visible. Scanning probe microscopy (SPM) revealed that the bump defects had locally higher electrical conductivity (above 70 nA) than the surrounding SiC matrix both after implantation at 500 °C and after annealing at 1600 °C. Lower electrical conductivity (below 1 nA) was observed for the saucer-pit defects. The formation of the specific strain fields around the macro-defects and the appearance of implantation-driven high electrical conductivity at the bump defects are discussed on the basis of the SPM observation and electron probe microanalysis.

Highlights

Due to their excellent structural, chemical, and mechanical stability, silicon carbide (SiC) devices have been expected to be available in automobile, electrical, and communication industries
we observed the specific local strain fields around the macro-defects
The strain field covered the isotropic spread from the macro-defects in the SiC samples implanted at

Summary

INTRODUCTION

Due to their excellent structural, chemical, and mechanical stability, silicon carbide (SiC) devices have been expected to be available in automobile, electrical, and communication industries. It is well known that damage resulting from lattice defects such as vacancies and interstitials are induced in the SiC crystal during implantation.. In order to recover the damage in the implanted region and activate implanted impurities electrically, high-temperature implantation at several hundred degrees Celsius and postimplantation annealing at 1500 C and above are usually conducted. We report on the structural changes of defects in 4H-SiC caused by high-temperature Pþ-implantation and annealing. We found that the origins of these specific defect images were small bump and saucer-pit defects, generally called “macro-defects,” which were originally located on the initial surface of the SiC epilayer. Scanning probe microscopy (SPM) revealed that the electrical properties of the bump defects changed during high-temperature implantation and annealing, together with their structural change. Were attributable to the changes in the elemental constituents of the defect surfaces

EXPERIMENTS

SUMMARY