Kinetics of the hydrogen effect on PbSe epitaxial films

Abstract

A one-dimensional diffusion equation has been solved to establish the kinetic behavior of atomic hydrogen in PbSe under both steady state a.c. hydrogen excitation and initial step conditions. The boundary conditions on the surfaces of the films were constructed with the surface recombination velocity g as a phenomenological parameter. Since the hydrogen effect makes the film more n-type, measurements of electrical conductivity changes were used to determine the amount of atomic hydrogen inside the film. Step and periodic hydrogen flux-time variations were used to determine g and the diffusion coefficient D, respectively. g was linearly proportional to the partial oxygen pressure. The activation energy for H diffusion was 0.4 eV and the pre-factor was 1.1×10 −7 cm 2 sec −1 for the p-type films measured. The assumed boundary conditions for the analysis were established as a result of the experimental measurements. The amount of atomic hydrogen that diffused into the conventional vacuum evaporated p-type epitaxial PbSe films was much larger than that which diffused into an n-type epitaxial film grown by the hot wall method. This result strongly suggests that the hot-wall-grown film had fewer Pb vacancies than the vacuum-evaporated films.