Laser irradiation of compensation doped hydrogenated amorphous silicon

A Q-switched ruby laser was used to study both reversible and permanent changes in the electrical conductivity of partially compensated n-type and p-type hydrogenated amorphous silicon (a-Si:H). This method of illumination provides an accelerated test of the magnitude of reversible photoinduced changes (known as the Staebler-Wronski effect) if the laser beam energy is insufficient to produce gross structural alterations in the samples. Compensated films are less susceptible to Staebler-Wronski changes than are single doped films. At energy densities above about 0.2 J cm^-2, recrystallization of these thin films occurs, to an extent dependent on the energy. Energies above about 1.2 J cm^-2 produced no further increases of conductivity. The total increase in conductivity over this energy range was 10⁴-10⁵ for p-type films and 10³-10⁴ for n-type films giving similar saturated conductivity values for both series of films. There were also large improvements in photosensitivity.