Papers by Author: S.I. Maximenko

Abstract: More than fifty years ago Frank proposed that a dislocation with a Burgers vector larger than a critical value would have an open core. Since then, there has been controversy as to whether micropipes in SiC are examples of open core screw dislocations. In this work open core dislocations in 4H-SiC material are investigated by AFM. The results are interpreted on the basis of Frank’s theory and the surface energy of SiC is estimated from the critical value of Burgers vector. Finally, the extracted surface energy is compared with the results of other research.

Abstract: In this work, we investigated the effect of crystal defects on reverse I-V characteristics of avalanche photodiodes (APDs) using electron-beam induced current (EBIC) mode of SEM. Two types of SiC APD structures (I and II) were fabricated using 2 inch p-doped substrates with n-doped epilayers and 3 inch n-doped substrates with p- and n- epilayers. Areas of the formed diodes were approximately 1 mm2. The devices without any kind of electrically active 3-D structural defects demonstrated breakdown voltages close to theoretical values, ~500 V for the APD Type I and ~1200 V for Type II APD. Stability of Type I devices was tested by applying a short pulse of high voltage (~800 V). EBIC images, taken prior to and after the failure test, showed new defects in the dislocation free area, which, presumably, were caused by thermal breakdown.

Abstract: The nucleation sites of stacking faults (SFs) during forward current stress operation of 4H-SiC PiN diodes were investigated by the electron beam induced current (EBIC) mode of scanning electron microscopy (SEM), and the primary SF nucleation sites were found to be basal plane dislocations (BPDs). Damage created on the diode surface also acts as SF nucleation sites. By using a novel BPD-free SiC epilayer, and avoiding surface damage, PiN diodes were fabricated which did not exhibit SF formation under current stressing at 200A/cm2 for 3 hours.

Abstract: In this paper the electrical activity of stacking faults and that of their bounding partial dislocations in degraded PiN diodes has been investigated by the technique of electron beam induced current (EBIC). The recombination behavior of C- and Si-core dislocations is discussed. It is proposed that nonradiative recombination significantly exceeds radiative recombination on both the C- and Si-core partial dislocations. At the same time, predominantly radiative recombination takes place in the faulted planes that presumably act as quantum wells.

Abstract: The degradation of diffused SiC PIN diodes during forward-biased operation was studied by first fabricating PIN diodes by diffusion of aluminum or boron into 4H-SiC substrates with n-type 10-15 µm thick epilayers doped by nitrogen up to 5x1015cm-3. The formed diodes were subjected to degradation testing under an applied current density of 200A/cm2 at room temperature. The majority of the Al diffused diodes demonstrated a voltage drift, ΔVf, of more than 2 V, while B-doped diodes showed no significant change in forward voltage. The EBIC mode of SEM was employed to monitor nucleation and expansion of stacking faults.