Laser-induced damage to semiconductors

An experimental study has been made of the damage to p-type silicon caused by a normal and a Q-switched ruby laser. For the normal laser irradiation, the crack-line formation was due to thermal stress. For the Q-switched laser irradiation, cracks extending into the volume of the crystal were produced at a high power density of about 350 MW cm -2 . The damage threshold was almost independent of the mechanical damage depth and the ratio of the damage threshold for a mechanically lapped sample to that for a chemically polished one (I K /I D ) was only about 1 / 2 approximately 1 / 3 . The damage induced in GaP whose forbidden-band width is greater than the photon energy was also investigated.