PRINCIPLES or TKANSISTOR ACTIO.X 277 



24. This instrument was designed and built by H. R. Moore, who aided the authors a 



great deal in connection with instrumentation and circuit problems. 



25. The surface had been o.xidized, and ])otential probe measurements (ref. (2)) gave 



evidence for considerat)le surface conductivity. 



26. Measured between centers of the contact areas. 



27. Potential probe measurements on the same surface, given in reference (2), gave 



evidence of surface conductivity. 



28. Unpublished data. 



29. J. H. ScalY, H. C. Theuerer, and E. E. Schumacher, "P-type and N-type Silicon and 



the Formation of the Photovoltaic Barrier in Silicon" (in publication). 



30. G. L. Pearson and J. Bardeen, PZ/ys. Rev. March 1, 1949. 



31. See, for example, reference 6, Chap. 3. 



32. K. Lark-Horovitz, A. E. Middleton, E. P. Miller, and I. Walerstein, Pliys. Rev. 



69, 258 (1946). 



33. Hall and resistivity data at the Bell Laboratories were obtained by G. L. Pearson 



on samples furnished bv J. H. Scat^" and H. C. Theuerer. Recent hall measure- 

 ments of G. L. Pearson'on single crystals of n- and p-type germanium give values 

 of 2600 and 1700 cm-/volt sec. for electrons and holes, respectively at room tem- 

 perature. The latter value has been confirmed by J. R. Haynes by measurements 

 of the drift velocity of holes injected into n-type germanium. These values are 

 higher, particularlv for electrons, than earlier measurements on polycrystalline 

 samples. Use of the new values will modify some of the numerical estimates made 

 herein, but the orders of magnitude, which are all that are significant, will not be 

 affected. W. Ringer and H. Welker, Zeits. f. Naturforschung, 1, 20 (1948) give 

 a value of 2000 cmVvolt sec. for high resistivity w-type germanium. 



34. See R. H. Fowler, Statistical Mechanics, 2nd ed., Cambridge University Press, 



London (1936). 



35. From unpublished data of K. M. Olsen. 



36. N. F. Mott, Proc. Ro\: Soc, 171A, 27 (1939). 



37. W. Schottkv, Zeits. f. Phys., 113, 367 (1939), Pliys. Zeits., 41, p. 570 (1940), Zeits 



f. Pliys., 118, p. 539 (1942). Also see reference 18. 



38. See reference 6, Chap. 4. 



39. S. Benzer, Progress Report, Contract No. W-36-039-SC-32020, Purdue Umversity, 



Sept. 1-Nov. 30. 1946. 



40. S. Benzer, Phys. Rev., 71, 141 (1947). 



41. Further evidence that the barrier is internal comes from some unpubbshed experi- 



ments of J. R. Haynes with the transistor. Using a fi.xed collector point, and 

 keeping a fixed distance between emitter and collector, he varied the material 

 used for the emitter point. He used semi-conductors as well as metals for the 

 emitter point. While the impedance of the emitter point varied, it was found 

 that equivalent emitter currents give changes in current at the collector of the same 

 order for all materials used. It is believed that in all cases a large part of the for- 

 ward current consists of holes. 



42. The space charge of the holes in the inversion region of the barrier layer is neglected 



for simphcity. 



43. Reference 6, Chap. 4. 



44. S. Benzer "Temperature Dependence of High Voltage Germanium Rectifier D.C. 



Characteristics," N.D.R.C. 14-579, Purdue Univ., October 31, 1945. See refer- 

 ence 6, p. 376. 



45. See, for example, E. H. Kennard, Kinetic Theory of Gases, McGraw-Hill, Inc., New- 



York, N. Y. (1938) p. 63. 



46. Reference 6, p. 377. 



47. Obtained by plotting log ,? versus s^/Ic- This plot is not a straight line, but has an 



ujoward curvature corresponding to an increase in t with separation. The value 

 given is a rough average, corresponding to s^Ic the order of 10^' cm^, amp. 



48. One mav expect that the mobility will depend on field strength when the drift veloc- 



itv is as large as or is larger than thermal velocity. Since ours is a borderline case, 

 the calculation using the low field mobility should be correct at least as to order of 

 magnitude. 



