# D-Defects Detected by ELYMAT Technique

| With the ELYMAT (a special technique to map minority carrier lifetime in Si; see the publications in the link), D-defects and other microdefects in Si can be "seen" in some cases because they decrease the minority carrier life time (they act as recombination centers).
|  | The pictures obtained monitor the local photo current (induced by a scanned Laser beam) in special electrolytic junctions. It is a direct measure of the minority carrier life time. A typical picture of state-of-the-art as-grown 150 mm Si wafers from around 1990 is shown below. Bright areas correspond to decreased life times.
|  | The most outstanding feature is the well-defined ring. It is due to small defects incorporating SiO2.
|  | With hindsight gained by much research in the nineties, the situation is as follows: Inside the oxygen-precipitate ring, small vacancy agglomerates (in the form of octahedral little voids) dominate; outside the ring, interstitials agglomerates (probably in the form of small stacking faults and dislocation loops (the old "classical" swirl defects)) were formed.
| This rather unique defect pattern is the result of the complicates interaction of three main point defects: vacancies, Si-interstitials and O-interstitials. Whereas the above interpretation is now universally accepted, the details about the primary defects are not yet known beyond reasonable doubt.
|  | For a recent review read the paper of Bob Falster and V.V. Voronkov.

With frame

1.3.3 The larger View and Complications

© H. Föll (Defects - Script)