CHEMICAL INTERACTIONS AMONG DEFECTS IN Ge AND Si 553 



Table II 



pending on the temperature, the specimen surface was lapped smooth 

 with carborundum paper. Resistivities were then measured by means of 

 a two point probe. 



Table II collects the data showing T, the temperature of saturation 

 in degrees centigrade, po the resistivity before saturation, .4" the gallium 

 concentration computed from po, p the resistivity after saturation, and 

 D^ the lithium concentration computed from p. The final column shows 

 Do"^ computed using (4.1) and Fig. 2. 



In Table II the 25°C value of Dq^ has been taken as the value com- 

 puted in section III in connection with Fig. 4. It might be thought (in 

 view of a later section in this paper) that the 25° and 100°C values of 

 Do are not as reliable as the others because at the low temperatures 

 involved the solubility of lithium may be influenced by ion pairing as 

 well as electron-hole equilibria. However, Appendix A shows that the 

 possible error is small. 



In Fig. 5 Dq^ is plotted against temperature using these data. The plot 

 is the curve labeled GaT = 0, and the open circles were obtained by in- 

 serting the measured D^ values (crosses) into (4.1). We notice that the 

 curve has a maximum in the neighborhood of 600°C. The occurrence of 

 a maximum, is a necessity if Dq^ is to pass to zero, as it must at the 

 melting point of germanium. It is also worth noticing that Do"*" near 

 room temperature lies in the range of order 10^^ cm~^, but that its meas- 

 urement has been effected at concentrations as high as 10^^ cm~^ This 

 ! illustrates another application of the electron-hole equilibrium, namely 

 in the determination of solubilities. 



\18 



and 10 cm 



This 



3 



With Do in our possession it is interesting to return to (3.4) and to 



calculate D^ as a function of temperature for various levels of A 



has been done for values of A" equal to 10^^ 10^ ^ 10^^, 



The curves so obtained appear in Fig. 5, labeled Ga" = 10'", 10'°, 10 



1 10 cm" , respectively. Their most striking common feature is the mini- 



I mum which appears below 200°C. This minimum introduces a new prob- 



<i& 



17 



