SINGLE CRYSTAL BY ZONE LEVELING 657 



Fig. 11. — Photograph of zone leveled single crystal ingot. 



the same Cl , provided that the zone vokime is accurately reproduced. 

 In this way it is readily possible to resume leveling as before and hence 

 virtually to reproduce a desired resistivity. For the small k solutes, 

 In and Sb , discussed in this paper the loss of d in one leveling run is so 

 small as to be insignificant compared to other sources of error in this 

 quantity. 



' PILOT PRODUCTION RESULTS 



The capabilities of the zone leveling equipment and techniques just 

 I described may be evaluated with reasonably good accuracy on the basis 

 1 of the measurement results obtained from more than 300 single crystal 

 1 ingots so produced. Over 200 of these crystals were grown in the after- 

 heater at the "slow" growth rate of 0.09 mils per second. The rest were 

 I grown with a short after-heater or none at all at a growth rate about ten 

 times greater. 



The ingots to be measured (see Fig. 11) were usually 4-6 inches long 

 after removing seeds and solidified zones (i.e., 2-3 zone lengths), and 

 were cut into 1 inch lengths. The p, r, and e measurements were taken 

 ^ on the flat ends of these segments. The results of the observations will 

 ' be summarized and discussed in terms of the four device test require- 

 ments described earlier. 



(1) Compositional Uniformity 



The resistivity measurements were taken with a calibrated 4-point 

 probe technique at five locations on each ingot cross-section (center, top, 

 bottom and each side). The spacing between adjacent points of the probe 

 was 50 mils. Accordingly, these measurements would be insensitive to p 

 fluctuations in the material of this order or smaller. However, an investi- 

 gation by potential probing techniques, of Ge filaments cut from zone 

 leveled ingots indicates that p fluctuations in zone leveled material are 



'6 L. B. Valdes, Proc. I.R.E., 42, p. 420, 1954. 

 " Erhart, D. L., private communication. 



