DIFFUSED EMITTER AND BASE SILICON TRANSISTORS 



10" 



17 



10 



H 



Ta 



10 



10 



0.1 



0.2 



0.3 



0.4 



0.5 



0.6 



0.7 



Fig. 11 — ^Dependence of emitter efficiency upon diffusant surface concentra- 

 tions and diffusion lengths. The lines of constant /2//1 are essentially lines of 

 constant emitter efficiency. The ordinate is the ratio of surface concentrations of 

 the two diffusants and the abscissa is the ratio of their diffusion lengths. 



/2//1 = — 1.0 corresponds to a 7 of 0.75 and /2//1 = —0.01 corresponds 

 to a 7 of 0.997. 



4.. 3 Base Resistance 



It was indicated above that I2 depends principally on r2 and X. Fig. 12 

 is a plot of the constant I2 contours in the r2 — X plane for I2 in the range 

 from —10^ to —10. The graph is for Ti/To = 10. The base layer sheet 

 conductivity, cjb , can be calculated from these data as 



Qb = —qtihTjiNz 



(4.5) 



where q, L\ and A^3 are as defined above and /I is a mobility properly 

 weighted to account for impurity scattering in the non-uniformly doped 

 base region. The units of gb are mhos per square. 



