Growth and Properties of Micro-Crystalline (Si,Ge):H Films

Abstract

ABSTRACTThis paper reports on the growth and characterization of micro-crystalline (Si,Ge) films deposited on glass and polyimide substrates. The films were grown using a hydrogen diluted remote ECR plasma process. The feedstock gases were silane and germane. The entire range of composition from 100% Si to 100% Ge was studied. A low-pressure, low-substrate temperature, and high-power environment was used to change the morphology from amorphous to micro-crystalline. The films deposited at 5 mT pressure are generally micro-crystalline. The film's structure was studied using Raman spectroscopy. Raman spectra show clear, sharp crystalline-type Si and Ge peaks. Electronic properties of the films, such as activation energy and absorption constant down to α = 1 cm−1 were also measured. The sub-gap absorption data also show crystalline absorption behavior, with the absorption shifting to lower energies as the Ge content is increased. This absorption data shows that the materials have low defect densities.