DISTRIBUTION AND CROSS-SECTIONS OF GERMANIUM SURFACES 1053 



200 



m 



20 



10 



8 



7 

 -6 



-5 



-4 



-3 



-2 



-1 



Y-lnX, 



Fig. 3 — Experiment and theory for surface recombination. Solid curve theory 

 circles and dots for n and p-type samples, respectively. 



our estimates for ap and o-„ appear to be of the expected order of magni- 

 iitudes lends strong support to the view that identifies the traps appear- 

 ing in the field-effect and surface photo-voltage experiments with those 

 responsible for surface recombination. 



The result that (o-p/cr„) = 150 is good evidence that the fast states are 

 acceptor-like. This statement must be restricted to the range \ v \ < 4; 

 the states that are outside this range might be of either type. Also one 

 might allow a rather small fraction of the states near the middle to be 

 donor- type, without serious trouble; but the experimental results compel 

 one to believe that most of the fast states within 0.1 volts or so of the 

 centre of the gap are acceptor-like. 



V. TRAPPING KINETICS 



The foregoing considerations have concerned the steady-state solution 

 to the siu'face trapping problem. If the experimental constraints are 

 changed sufficiently rapidly, however, there may be effects arising from 

 the finite time required for the charge in surface states to adapt itself 



