Correlation between Optical and Electrical Properties of the Pulsed-Laser Deposited Amorphous Films of Germanium

Abstract:

Amorphous films of germanium (thicknesses 25 - 450 nm) were obtained on glass substrate at room temperature by the vacuum (residual gas pressure 3´10-6 mm Hg) pulsed-laser (Q-switched glass: Nd3+ laser (1.064 µm wavelength, 30 ns pulse duration, laser energy - 3 J per pulse, laser intensity on Ge target ~109 W/cm2)) deposition method. The comprehensive study of the optical and electrical properties of amorphous films of germanium showed the presence of two types (A and B) of films with different characteristics. With increasing of film thickness from 100 nm to 450 nm we observe the transition from the prevailing topological disorder (A- type) to the quantify disorder (B- type) in the region of 300-350 nm. Thicker films are characterized by a more homogeneous “network” of bonds, which minimizes the number of defects and localized states in the “forbidden” gap and, consequently, increases the resistivity and optical gap. An increase of the resistivity and optical gap is observed with decreasing film thickness (< 100 nm), which is explained by an increasing influence of natural oxidation of thin films. The results of temperature measurements for A- type films shows that the temperature dependence of resistivity is characterized by Mott's law (lnρ ~ T-1/4) in the temperature range of 100-240 K, while for B- type it indicates an activation character (lnR ~ ΔEa/kT) in the temperature range of 150-350 K.

• Periodical: Applied Mechanics and Materials (Volume 248)
• Pages: 320-324
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.248.320
• Online since: December 2012
• Authors: Karapet Avjyan, Ashot Khachatryan, Lenrik Matevosyan, Arsen Mkrtchyan, Gevorg Vardanyan
• Keywords: a-Ge Films, Electrical Properties, Optical Property, Pulsed-Laser Deposition

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