Optical investigations of recombination processes in laser-annealed and thermally-annealed semiconductors

Electron-beam-induced current (EBIC) and low-temperature photoluminescence have been used to study minority-carrier recombination processes in ion-planted Si subjected to scanned laser or electron beam annealing. Dark stripes parallel to the laser scanning direction always appear in the EBIC display of laser-annealed samples. The contrast of these dark stripes increases with laser power, while the charge collection efficiency decreases. Both EBIC and photoluminescence results indicate that damage is induced by the annealing laser beam, and that this laser-induced damage extends several microns below the implanted layer. On the other hand, electron-beam annealing yields a laterally uniform pattern and superior charge collection efficiency. Deep Level Transient Spectroscopy (DLTS) is also used to study deep deflect levels in beam annealed silicon. A dominant hole (E sub Y + 0.45 eVO) was observed in CW laser-annealed samples immediately after sample preparation. In contrast, only a low concentration of hole traps appears in electron-annealed Si. By correlating these results with published literature, the laser-induced quenched-in defects are identified as interstitial Fe and Fe-B pair reactions in Si. Possible sources of Fe in Si will be discussed.