Focused Laser and Related Techniques

A focused laser may be used for drawing or for drilling microstructures into semiconductor surfaces, in these cases, the laser beam is focused into a spot onto the crystal surface. Specific patterns may be generated by computer-controlled scanning techniques. 

Osgood and co-workers at Columbia University (10)(21)(22) have investigated laser hole drilling in crystals of lll-V compounds simply 

Rauh and LeLievre (24) examined the intensity and total delivered energy dependence of hole diameters etched in n-GaAs with a focused 633 nm (HeNe laser) source. Unlike the results with ultraviolet excitation, the hole diameters grew sharply with etching time and no light guided structures were produced. However, shallow pits could be etched with 

A common feature of the hole drilling experiments described above is that they were performed without electrochemical control of the semiconductor surface. As a result, quantum yields were always much less than unity and thewidth of the space charge region was probably very low. The latter factor doubtlessly magnified differences between quantum yields observed for ultraviolet and visible light resulting from differences in the penetration depth and hence efficiency of electron-hole separation. T o date, no studies of the effects of electrode bias on the rates and profiles of laser drilled structures have been presented. 

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