474 BELL SySTE^r TECHNICAL JOURNAL 



There is no good theoretical reason to expect that a is different from unity 

 for small current flow in normal contacts unless trapping is important. 



Equation (8) is used as the basis for the analysis of the low-voltage 

 data. One important consequence of the equation is that if />„ is different 

 from zero, there is a voltage drop across the barrier layer even though 

 no net current flows to the point. The presence of the added holes in the 

 interior produces a floating potential on the point. The magnitude of this 

 floating potential, Vcf, is obtained by setting / = in Eq. (8) and find- 

 ing the value of Vc which solves the equation. This potential can be 

 observed on a voltmeter and is analogous to a photovoltage. 



Associated with the floating potential is a change in conductance of 

 the contact. The conductance near 7 = 0, given by 



G = (rf//JFe)r,=V,, = (dh/dV,)y^^y^,, (9) 



is just the conductance for normal hole concentration in the interior at an 

 applied voltage equal to Vc/. In setting the conductance equal to the 

 derivative of / with respect to Vc, we have neglected the difference, 

 Vi, between Vc, the voltage drop across the barrier, and Vf, the total 

 drop from the contact to the interior. This corresponds to neglecting the 

 spreading resistance in comparison with the barrier resistance. 



Equation (8) may be used to relate the floating potential with change 

 of conductance of the contact. The appropriate equations, together with 

 applications to data of Pearson and of Brattain, are given in Section II. 

 In Section III we derive Eq. (4) which relates the added hole current 

 with the added hole concentration in the interior. This relation is used 

 to show that the point conductance G varies linearly with the added hole 

 concentration, /?„. The theoretical expression for conductance is comj^ared 

 with data of Pearson and of Suhl. 



In section IV we discuss the dependence of the current-voltage char- 

 acteristic at large reverse voltages on hole concentration. I'nder these 

 conditions it is the electric held rather than diffusion which produces the 

 hole current in the body of the germanium. The electron and hole currents 

 are then in the ratio of the electron to hole conductivity. With introduc- 

 tion of an "intrinsic a" for the contact, a simple relation is derived for the 

 dependence of current on hole concentration for fixed voltage on the 

 point. This relation is used to determine a for several point contacts from 

 some data of J. R. Haynes. 



II. Elo.\ting Potentiat- of Point Contact 



In order to get analytic expressions for the floating potential and ad- 

 mittance, it is necessary to make some assumption about the normal cur- 



