Short minority carrier lifetimes in highly nitrogen-doped 4H-SiC epilayers for suppression of the stacking fault formation in PiN diodes

Abstract

We investigated the dependency of minority carrier lifetimes on the nitrogen concentration, temperature, and the injected carrier concentration for highly nitrogen-doped 4H-SiC epilayers. The minority carrier lifetimes greatly shortened when the nitrogen concentration exceeded 1018 cm−3 through enhancing direct band-to-band and Auger recombination and showed a slight variation in the temperature range from room temperature (RT) to 250 °C. The epilayer with a nitrogen concentration of 9.3 × 1018 cm−3 exhibited a very short minority carrier lifetime of 38 ns at RT and 43 ns at 250 °C. The short minority carrier lifetimes of the highly nitrogen-doped epilayer were confirmed to maintain the values even after the subsequent annealing of 1700 °C. 4H-SiC PiN diodes were fabricated by depositing a highly nitrogen-doped epilayer as a “recombination enhancing layer” between an n− drift layer free from basal plane dislocations and the substrate. The PiN diodes showed no formation of stacking faults and no increase in forward voltage during current conduction of 600 A/cm2 (DC), demonstrating that a highly nitrogen-doped buffer layer with a short minority carrier lifetime successfully suppresses the “bipolar degradation” phenomenon.

CVD growth and properties of on-axis vanadium doped semi-insulating 4H-SiC epilayers

“…No difference has been observed in these samples regarding electrical, optical and structural properties, indicating that V concentration is probably similar in both samples and V has a strong memory effect. It has been suggested that, in order to avoid the penetration of bipolar plasma into the substrate and hence the formation of stacking faults in SiC-based PiN devices, V doping can be used in the buffer layer to effectively kill bipolar plasma 25 . V has also shown to effectively control charge carrier lifetime in 4H-SiC epilayers, when used at very low and controlled concentration (<1x10 13 cm -3 ) 26 .…”

Origin and Generation Process of a Triangular Single Shockley Stacking Fault Expanding from the Surface Side in 4H-SiC PIN Diodes

“…The 1SSFs of T1 and T3 had a right-angled corner on the right side, and these two types are the most frequently observed and repo rted. 3,[5][6][7][9][10][11][12][13][14]16,[19][20][21][22] However, the 1SSFs of T2 had a triangular shape with a right-and-left in contrast to T1 and T3. The expansion direction of T2, which was from the surface to the substrate/epilayer interface, was opposite to that of T3.…”

“…4 Most previous studies on the expansion of 1SSFs have found that the SSFs originate from two kinds of BPDs: one that had penetrated from the substrate into the epilayer, 5,6 and another that had converted to a threading edge dislocation (TED) around the substrate/epilayer interface during epitaxial growth. 7 In addition, many analyses have been conducted of these 1SSFs, including current/temperature stress testing, [8][9][10][11][12][13][14] calculations, [15][16][17][18] and crystal analysis. [19][20][21][22][23] The BPD detection by photoluminescence (PL) imaging and the use of a buffer layer between the substrate and the epitaxial layer was proposed as a method for controlling 1SSF expansion 4,7,11,24 with the aim of solving the V F degradation issue.…”

“…7 In addition, many analyses have been conducted of these 1SSFs, including current/temperature stress testing, [8][9][10][11][12][13][14] calculations, [15][16][17][18] and crystal analysis. [19][20][21][22][23] The BPD detection by photoluminescence (PL) imaging and the use of a buffer layer between the substrate and the epitaxial layer was proposed as a method for controlling 1SSF expansion 4,7,11,24 with the aim of solving the V F degradation issue.…”

Suppression of stacking fault expansion in a 4H-SiC epitaxial layer by proton irradiation

“…To suppress 1SSF expansion, proper design of the buffer layer, which is the first thin layer grown on a substrate, is important. Tawara et al have clearly demonstrated the relationship between the injected carrier concentration and 1SSF expansion, and showed that a recombination-enhancing buffer layer in p-i-n diodes suppresses 1SSF expansion 33 , 34 . However, a thick buffer layer is necessary to suppress 1SSF expansion under a high current density, resulting in an increased process cost.…”