Structural defects in electrically degraded 4H-SiC p+/n−/n+ diodes

Abstract

Triangular structural defects are occasionally generated during the long-term operation of 4H-SiC pin diodes and degrade the forward characteristics of the diode. We have used synchrotron white beam x-ray topography, scanning electron microscopy, in situ cathodo luminescence, and transmission electron microscopy to characterize the structure and formation of these defects. It is shown that the defects are stacking faults on the (0001) basal planes, bound by partial dislocations with Burgers vectors 1/3〈101̄0〉 and 1/3〈011̄0〉. These partials are suggested to form by the dissociation of existing dislocations.

Influence of Temperature on Shockley Stacking Fault Expansion and Contraction in SiC PiN Diodes

“…A second model, which was proposed by various groups, stated that long-range stresses within the diode structure were causing the SSF propagation. [9][10][11] However, the results of Ha et al 12 clearly illustrated that, while stresses might influence SSF propagation, they clearly do not provide the driving force. At the same time they proposed a third model stating that the 3C-SiC structure of the SSF, not the native 4H-SiC lattice, was the thermodynamically favorable polytype and therefore the formation was driven by the improved thermodynamic stability of the 3C-SiC.…”

Opto-Electronic Study of SiC Polytypes: Simulation with Semi-Empirical Tight-Binding Approach

“…According to the calculation done by Persson et al (26), (38), the second CBM of 3C-SiC is at the same symmetry point (X) as the first one with 2.92 eV higher in energy and this was confirmed experimentally from optical absorption measurements with slightly larger energy difference ( 3.1 eV) between the two minima (13). Persson et al calculations also show that the three hexagonal polytypes (2H, 4H, 6H) have their second CBMs located at the M point and the energy difference between the first and second CBMs is 0.60 eV for 2H, 0.122 eV for 4H, and 1.16 eV for 6H respectively.…”

Cubic inclusions in 4H-SiC studied with ballistic electron-emission microscopy

“…Recently, the long-term stability issue of SiC devices has received much attention after it was discovered that stacking fault ͑SF͒ formation 2 during room-temperature electrical stressing of 4H-and 6H-SiC pn diode structures [3][4][5] or during high-temperature processing of 4H-SiC materials with heavily n-type epilayers 6 or substrates 7,8 caused significant changes to optical and electrical behavior. It was found that basal plane SFs in 4H-SiC host resulted in planar ''cubic inclusions,'' i.e., thin ͑Ͻ1.5 nm͒ sheets with cubic 3C local stacking embedded in the 4H-SiC host ͑in the electrically stressed diodes, all the inclusions observed by TEM were found to be of the ''single-SF'' type 5,9 while those observed in the high-temperatureprocessed material were all ''double-SF'' inclusions 6,8,10 ͒. It was proposed that these cubic inclusions should behave as unique ''structure-only'' electron quantum wells ͑QWs͒, 2,11-13 which are delimited only by a change in local stacking.…”