Photoluminescence Study of the Driving Force for Stacking Fault Expansion in 4H-SiC

Abstract

We investigated expansion velocities of Shockley stacking faults (SSFs) in 4H-silicon carbide under laser illumination using photoluminescence methods. The experiments showed that the velocity of SSF expansion or the glide velocity of SSF-bounding 30°-Si(g) partial dislocations (PD) is supralinearly dependent on the excitation intensity. We estimated sample temperature by analyzing the broadening of band-edge emission and concluded that the lattice heating by laser illumination is not the cause of the enhanced dislocation glide. The supralinear dependence can be accounted for by a photo-induced sign reversal of the effective formation energy of SSF acting as the driving force of SSF expansion under the illumination.

Expansion of Shockley stacking fault observed by scanning electron microscope and partial dislocation motion in 4H-SiC

“…Using this value and the lateral moving speed of the electron probe (<¼ 3 Â 10 À3 m/s), the magnitude of Dx for a line scan at the largest is estimated to be approximately 0.1 lm, which is sufficiently smaller than R. Therefore, it is confirmed that Dx was not given by R. The obtained PD velocity, 5 Â 10 À5 m/s, corresponds to the velocity in the case of irradiation at 1.2 Â 10 6 W/cm 2 , from the results shown in the literature. 19 The irradiation current was not measured in our experiments, but the estimated current from this power is approximately 4 lA, which is roughly plausible.…”

“…Previous research on SSF expansion or PD motion often employed imaging methods using electroluminescence, 11 photoluminescence, 14,18,19 cathodoluminescence, 20 or electronbeam-induced current. 20,21 In this paper, we report the observation of SSFs using secondary electron images, which is the most common mode of scanning electron microscopy (SEM) operation.…”

Photoluminescence Study of Radiation-Enhanced Dislocation Glide in 4H-SiC

“…The sample heating by the laser illumination ( 42 mW) was determined to be negligible based on the fitting of the free-exciton emission spectra to the theoretical Maxwell-Boltzmann shape. 10) The stacking-fault-related emission at 2.9 eV was selected using band-pass filters and its intensity mapping on the sample surface was obtained. First, the stacking fault was expanded to $2 mm in length from the indent by scanning the excitation laser in advance.…”

Annealing and LEEBI Effects on the Stacking Fault Expansion and Shrinking in 4H‐SiC

“…Thus, the above results clearly show that LEEBI enhances the dislocation mobility, however, nature of driving force is not so clear. When indentation is used as a source for dislocation nucleation, force acting on the leading partial dislocation, which drives the SSF expansion, in a common case consists of shear stress from indentation and the "quantum well action," which in turn can depend on an excitation level [21] and on the SSF size. A shear stress decreases with r approximately as r À2 .…”

“…It can be a shear stress applied to the crystal or/and the "quantum well action." At rather high excitation level by the laser beam a superlinear dependence of dislocation velocity on the laser intensity was observed, [21] which was explained by the excess carrier effect on the SSF effective formation energy, i.e. on the effective driving force.…”