Assuming an arbitrary distribution of space charge in the barrier layer of a rectifier, the general form of the current-voltage relation has been derived on both diode and diffusion theory. A connexion, valid for most barriers, between this characteristic and the capacitance-voltage curve has been pointed out, and it has been shown that the Sachs breakdown voltage can be deduced from the latter characteristic. The general relations have been applied to a barrier whose distribution of impurity centres is assumed to establish itself by a diffusion process. Its properties have been investigated, and it has been found that the
shapes
of the experimental d. c. characteristics, considered in a previous paper (Landsberg 1951
b
), are in the same good agreement with the hypothesis of this barrier as they are with the hypothesis of a Schottky barrier. The difficulties regarding the
constants of the rectifiers
, as obtained from the experimental curves, are, however, greatly alleviated if the present barriers rather than Schottky’s barrier is assumed. It has been shown that both barriers belong to a whole class of barrier layers whose d. c. and capacitance-voltage curves have the same
shape
as the corresponding curves for a Schottky barrier.
