Growth of CdTe∕Si(100) thin films by pulsed laser deposition for photonic applications

Abstract

Cadmium telluride (CdTe) has become one of the most useful and versatile photonic materials. While many applications require the highest quality material possible, others can sacrifice some degree of sample quality in favor of reduced fabrication costs. Here, we explore the deposition of CdTe thin films deposited on (100) silicon substrates in the absence of costly ultrahigh vacuum conditions. This inevitably leads to the deposition of films on silicon’s native oxide. The work presented here explores the trade-offs in sample quality as determined by a host of characterization techniques. The films were deposited using the pulsed laser deposition technique at relatively low growth rates and at an optimized substrate temperature of 300°C. X-ray diffraction data show only (111) oriented CdTe with rocking curve widths broadened due to the lack of an epitaxial relationship between the film and substrate. Atomic force microscopy images confirm that the films have a smooth surface morphology as was suggested by their mirrorlike appearance. Film quality was also analyzed using photoluminescence, positron annihilation spectroscopy, and ellipsometry. While structural deficiencies have been observed in these films, the optical properties are remarkably similar to those expected for high quality CdTe.