/>-/; ./r.VC77().V.S' /.V Sr.MKOXDCi'rORS 



477 



The corresiKJiuliu^ currcuL c\alualL'(l at .v = where p = pi e.\i)(/co/) = 

 {pn(/Vi'kT)exp{iu}l) is given by 



/ = -V 



d.v f/.v 



= -<//; 



- T + 



qji + icoTp)p 

 kTr, 



2Lr 



1 + fl + (2L,/L„ni + icoT,)y'- ' "'^ 

 (1 + i^Tp) 



- Ll ■ 1 + [1 + {2Lr/Lpn\ + icTpW ' "'' 



= Api\e . 



This is equivalent lo (■i.M) in Section 4. 



APPENDIX III 



Admittance for Two Layers 



We shall here treat a case in which there is a thin layer on the »-side of 

 the transition region in which recombination occurs much more readily 

 than deeper in the n-layer. The case of an infinitely thin plane, discussed in 

 Section 4, is a limiting case of this model. We shall suppose that the layer 

 extends from .v = — c to .^ = while .t > corresponds to the ;/-region. We 

 shall suppose that the potential in the layer is uniform with value \pi whereas 

 in the ;i-region it has value i/'2 . The lifetimes of holes will be taken ri and r-^ 

 in the two layers. The solutions for pi and po are evidently 



pi = pic + (-1 e + B e ) e 



p'l = pio -\- C e 



-^x+iut 



X < 



.V > 



where 



a = (1 + /cor,)''''/V£>ri ^ (1 + i^rxf'-fU 

 ^ = (1 + /coT,)''7VZ)r2 ^ (1 + /a;ro)''7^2. 



The boundary condition for continuity of /p , recjuired to avoid singularit}- 

 in difp/dx, is 



