Nature of electrically detected magnetic resonance in highly nitrogen-doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>6</mml:mn><mml:mi>H</mml:mi></mml:mrow></mml:math>-SiC single crystals

This work focuses on unraveling electron paramagnetic resonance (EPR) and electrically detected magnetic resonance (EDMR) properties of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>n</a:mi></a:math>-type <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>6</b:mn><b:mi>H</b:mi></b:mrow></b:math> silicon carbide (SiC) single crystals with high concentrations of uncompensated nitrogen (N) donors, which is essential for fundamental understanding of spin-related phenomena, developing spin-based devices, optimizing materials and devices, and advancing research in quantum information and spintronics. Utilizing low-temperature multifrequency EPR spectroscopy (9.4–395.12 GHz), we identified two intense signals labeled as S line and S1 line in the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>6</c:mn><c:mi>H</c:mi></c:mrow></c:math>-SiC crystals with <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>N</d:mi><d:mi mathvariant="normal">D</d:mi></d:msub><d:mo>–</d:mo><d:msub><d:mi>N</d:mi><d:mi mathvariant="normal">A</d:mi></d:msub><d:mo>≈</d:mo><d:mn>8</d:mn><d:mo>×</d:mo><d:msup><d:mrow><d:mn>10</d:mn></d:mrow><d:mn>18</d:mn></d:msup></d:mrow></d:math> and <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mn>4</g:mn><g:mo>×</g:mo><g:msup><g:mrow><g:mn>10</g:mn></g:mrow><g:mn>19</g:mn></g:msup><g:mspace width="0.16em"/><g:mi mathvariant="normal">c</g:mi><g:msup><g:mrow><g:mi mathvariant="normal">m</g:mi></g:mrow><g:mrow><g:mo>−</g:mo><g:mn>3</g:mn></g:mrow></g:msup></g:mrow></g:math>. In addition, in <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:mn>6</k:mn><k:mi>H</k:mi></k:mrow></k:math>-SiC crystals with <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:msub><l:mi>N</l:mi><l:mi mathvariant="normal">D</l:mi></l:msub><l:mo>–</l:mo><l:msub><l:mi>N</l:mi><l:mi mathvariant="normal">A</l:mi></l:msub><l:mo>≈</l:mo><l:mn>8</l:mn><l:mo>×</l:mo><l:msup><l:mrow><l:mn>10</l:mn></l:mrow><l:mn>18</l:mn></l:msup><l:mspace width="0.16em"/><l:mi mathvariant="normal">c</l:mi><l:msup><l:mrow><l:mi mathvariant="normal">m</l:mi></l:mrow><l:mrow><l:mo>−</l:mo><l:mn>3</l:mn></l:mrow></l:msup></l:mrow></l:math>, a low-intensity triplet from N donors substituting the quasicubic “k2” nonequivalent position (<r:math xmlns:r="http://www.w3.org/1998/Math/MathML"><r:msub><r:mi mathvariant="normal">N</r:mi><r:mrow><r:mi mathvariant="normal">k</r:mi><r:mn>2</r:mn></r:mrow></r:msub></r:math>) was observed. The S line <u:math xmlns:u="http://www.w3.org/1998/Math/MathML"><u:mrow><u:mo>[</u:mo><u:msub><u:mi>g</u:mi><u:mi>⊥</u:mi></u:msub><u:mo>=</u:mo><u:mn>2.0029</u:mn><u:mrow><u:mo>(</u:mo><u:mn>2</u:mn><u:mo>)</u:mo></u:mrow><u:mo>,</u:mo><u:mspace width="0.16em"/><u:msub><u:mi>g</u:mi><u:mo>∥</u:mo></u:msub><u:mo>=</u:mo><u:mn>2.0038</u:mn><u:mrow><u:mo>(</u:mo><u:mn>2</u:mn><u:mo>)</u:mo></u:mrow><u:mo>]</u:mo></u:mrow></u:math> was assigned to the exchange interaction of conduction electrons and <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"><w:msub><w:mi mathvariant="normal">N</w:mi><w:mrow><w:mi mathvariant="normal">k</w:mi><w:mn>2</w:mn></w:mrow></w:msub></w:math>, while the S1 line <z:math xmlns:z="http://www.w3.org/1998/Math/MathML"><z:mrow><z:mo>[</z:mo><z:msub><z:mi>g</z:mi><z:mi>⊥</z:mi></z:msub><z:mo>=</z:mo><z:mn>2.0030</z:mn><z:mrow><z:mo>(</z:mo><z:mn>2</z:mn><z:mo>)</z:mo></z:mrow><z:mo>,</z:mo><z:mspace width="0.16em"/><z:msub><z:mi>g</z:mi><z:mo>∥</z:mo></z:msub><z:mo>=</z:mo><z:mn>2.0040</z:mn><z:mrow><z:mo>(</z:mo><z:mn>2</z:mn><z:mo>)</z:mo></z:mrow><z:mo>]</z:mo></z:mrow></z:math> is caused by the exchange spin coupling of localized N donors at the “k1” and “k2” positions. The S1 line was observed in high-frequency EDMR spectra of <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML"><bb:mrow><bb:mn>6</bb:mn><bb:mi>H</bb:mi></bb:mrow></bb:math>-SiC with <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML"><cb:mrow><cb:msub><cb:mi>N</cb:mi><cb:mi mathvariant="normal">D</cb:mi></cb:msub><cb:mo>–</cb:mo><cb:msub><cb:mi>N</cb:mi><cb:mi mathvariant="normal">A</cb:mi></cb:msub><cb:mo>≈</cb:mo><cb:mn>8</cb:mn><cb:mo>×</cb:mo><cb:msup><cb:mrow><cb:mn>10</cb:mn></cb:mrow><cb:mn>18</cb:mn></cb:msup><cb:mspace width="0.16em"/><cb:mi mathvariant="normal">c</cb:mi><cb:msup><cb:mrow><cb:mi mathvariant="normal">m</cb:mi></cb:mrow><cb:mrow><cb:mo>−</cb:mo><cb:mn>3</cb:mn></cb:mrow></cb:msup></cb:mrow></cb:math>, and its emergence was explained by an enhancement of the hopping conductivity due to the EPR-induced temperature increase mechanism. No EDMR spectra were found to occur in the <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML"><ib:mrow><ib:mn>6</ib:mn><ib:mi>H</ib:mi></ib:mrow></ib:math>-SiC crystals with <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML"><jb:mrow><jb:msub><jb:mi>N</jb:mi><jb:mi mathvariant="normal">D</jb:mi></jb:msub><jb:mo>–</jb:mo><jb:msub><jb:mi>N</jb:mi><jb:mi mathvariant="normal">A</jb:mi></jb:msub><jb:mo>≈</jb:mo><jb:mn>4</jb:mn><jb:mo>×</jb:mo><jb:msup><jb:mrow><jb:mn>10</jb:mn></jb:mrow><jb:mn>19</jb:mn></jb:msup><jb:mspace width="0.16em"/><jb:mi mathvariant="normal">c</jb:mi><jb:msup><jb:mrow><jb:mi mathvariant="normal">m</jb:mi></jb:mrow><jb:mrow><jb:mo>−</jb:mo><jb:mn>3</jb:mn></jb:mrow></jb:msup></jb:mrow></jb:math>, which is close to the critical donor concentration value for a semiconductor-metal transition. Thus it can be concluded that this N donor concentration is too high for the appearance of spin-dependent scattering and too low for the emergence of EPR-induced hopping mechanisms in <pb:math xmlns:pb="http://www.w3.org/1998/Math/MathML"><pb:mrow><pb:mn>6</pb:mn><pb:mi>H</pb:mi></pb:mrow></pb:math>-SiC. Published by the American Physical Society 2024