Influence of substrate materials on the properties of CdTe thin films grown by hot-wall epitaxy

Abstract

Growth of high-quality CdTe thin films by hot-wall epitaxy (HWE) under different temperature conditions and the control of their physical, electrical and structural properties have been examined by various ways. CdTe (1 1 0), Zn 0.04Cd 0.96Te (1 1 1), Hg 0.2Cd 0.8Te (1 1 1), Si (1 1 1) and BaF 2 (1 1 1) were used as substrates. The obtained films have the cut-off wavelength at 0.84−0.85 μm and the transmission of about 55–60% out of the fundamental absorption domain. The current–voltage investigations have shown that the contact properties strongly depend on the contact material and contact fabrication method and less depend on substrate materials. The film-specific resistances (4–7)×10 4 Ω cm were determined. The CdTe deposition (layer thickness about 1000 Å) on Cd x Hg 1− x Te resulted in significant increase in photodiodes electrical parameters. All samples showed the crystalline structure according to the XRD data with strong influence on lattice mismatch between CdTe and substrate materials. Atomic force microscope (AFM) investigations have shown a smooth and defect-free surface with a roughness range of 15–100 nm for 50 μm of basic length.