Experimental verification of the model by Klapper for 4H-SiC homoepitaxy on vicinal substrates

Abstract

4H-SiC homoepitaxial layers free of basal plane dislocations (BPDs) are urgently needed to overcome the so-called bipolar degradation of high-voltage devices. BPDs being present in substrates are able to either propagate to the epilayer or convert to harmless threading edge dislocations (TEDs) in the epilayer. The model by Klapper predicts the conversion of BPDs to TEDs to be more efficient for growth on vicinal substrates with low off-cut angle. This paper aims to verify the model by Klapper by an extensive variation of epitaxial growth parameters and the substrates' off-cut. It is shown that the off-cut angle is the key parameter for growth of BPD-free epilayers. Furthermore, it is shown that the model also describes adequately the behavior of different types of TEDs, i.e., TED II and TED III dislocations, during epitaxial growth. Therefore, the model by Klapper is verified successfully for 4H-SiC homoepitaxial growth on vicinal substrates. V C 2013 AIP Publishing LLC. [http://dx

In‐grown stacking‐faults in 4H‐SiC epilayers grown on 2° off‐cut substrates

“…The increasing demand for high performance and low cost SiC‐based devices is driving the development of epitaxy towards lower off‐cut angle substrates. This is motivated by the expected increase of the conversion rate of basal plane dislocations (BPDs) to threading edge dislocations and consequently, a reduction of the BPD density in epilayers using lower off‐cut angles . During long term forward operation of SiC bipolar devices using epilayers grown on off‐cut substrates, formation of stacking faults (SFs) results in an increased forward voltage drop which causes degradation of the device.…”

Rocking Curve Imaging Investigation of the Long-Range Distortion Field between Parallel Dislocations with Opposite Burgers Vectors

“…The dislocations we observe display a similar contrast and are nearly parallel to the c-axis. The threading dislocations parallel to the c-axis in 4H-SiC that have been reported [5,6] are either screw dislocations or edge dislocations displaying a Burgers vector along 1120. We discard the screw dislocation case because it is such that h.b = 0, h being the diffraction vector (perpendicular to the 4040 planes) and b the Burgers vector (parallel to c), and therefore, these dislocations should not be observed because they produce nearly no contrast in the image [16].…”

“…When this distance D is in the range 50-250 µm, we observe a weak (~µradian) distortion of the region lying between parallel dislocations with opposite Burgers vectors. Dislocations in 4H-SiC crystals have been extensively studied through X-ray diffraction Rocking Curve Imaging (see for instance [4][5][6][7][8][9]). The faint distortion we observe had not been investigated previously because there was no available experimental technique allowing its visualisation.…”

Erlangen—An Important Center of Crystal Growth and Epitaxy: Major Scientific Results and Technological Solutions of the Last Four Decades

“…It could be shown that the harmful BPDs can be converted into non‐dangerous threading edge dislocations (TED) during the epi‐process. The experimental findings could be explained by the so‐called Klapper model, showing that the off‐cut angle of the vicinal substrates is one of the most important parameters for improving BPD conversion. Based on experimental and theoretical results from different groups worldwide the off‐cut angle of the vicinal substrates was changed during that time in the whole SiC industry from 8° to 4° because of the related increase of the conversion probability for BPDs into TEDs during the epitaxial growth.…”