1216 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1956 



5. Plating the p-sidc of the p-ti Junction* 



This method detects and marks the junction in one process without 

 using the micrometer arrangement, ^^oltages are applied in such a way 

 that only the p-type side is plated (See Fig. 4). Since the plating pro- 

 jects up and is not optically flat, it can be recognized under the interfer- 

 ometer. It has the advantage of showing the junction as a line. The dis- 

 advantage is that it is only convenient on rectifying p-n junctions 

 (silicon), with n-type layers since the plating ought to take place on the 

 body side of the p-n junction. 



THE INTERFEROMETER 



The main part of the interferometer is a microscope with illumination 

 through the objective. As a source of monochromatic light, a sodium 

 lamp for which X = 5.89 X 10~^ cm is most convenient. The use of a 



Fig. 6 — Interferometer with light source. 



This method was developed by N. Holonyak. 



