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The films of amorphous germanium (a–Ge) were prepared by evaporation under high vacuum conditions (10) torr. The influence of various deposition rates within the range(2 – 10)Ǻ/sec on the dc electrical conductivity (σRT) and energy gap (Eg). The temperature dependence of conductivity for various deposition rates recorded in the range (303 – 503)K consist of two conduction regions within the temperature range (303–413)K and (413–503)K. From the absorbance spectrum Eg (energy gap) were obtained according to Tauce formula. It is found that Eg decreases from 1.08eV to 0.91eV when the rate of deposition increase from (2 – 10) Ǻ/sec while the electrical conductivity (σRT) increases from 1.28×10ֿ(Ώ.cm)ֿ1 to 11.53 ×10ֿ(Ώ.cm) respectively. Introduction Amorphous germanium has received relatively much less attention than the crystalline type because of the latter's greater technological importance. It has, however, been the subject of a number of investigation into it's structural, optical and electrical properties, because of the information it can contribute to understanding of other amorphous material more complex in molecular structure. Theoretical studies of amorphous semiconductors indicate that even though long-range order is not preserved, as long as the molecular bonds are not significantly disturbed, an energy band model is still applicable. The variability with preparation condition of most of the physical properties of amorphous Ge and Si films has for sometime been related to the presence of structural defects of variable nature and density in real amorphous networks. (2,3) These defects are expected to create large potential fluctuations which would essentially be responsible for high density of the localized states in the energy gap between the conduction and valence bands. Defects have generally been associated with the notion of dangling bonds, which may occur during the film formation when the local bonding requirements can not be fulfilled. There was submitted for consideration the influence of the technological parameters on the properties of the evaporated and sputtered amorphous germanium layers. The effect of the substrate temperature, residual atmosphere, annealing as well as influence of the material parameter seems to be the deposition rate, it influence on the electrical conductivity and optical energy gap of the evaporated (a–Ge ) layers. . The temperature dependences of the conductivity is approximated by the expression:      − σ = σ KT E exp a 0  (1) Where σ0 is the y-axis intercept for finite temperature, Ea is the activations energy c, and T is the absolute temperature. The optical absorption α(hν) of a-Si or aGe falls in three regions (9,10). 1. High absorption region. The interband phonon absorption has the highest absorption value (α ≥ 10 cm )and can be described as: ν − ν = ν α h ) E h ( B ) h ( 2 g  (2) where α is the absorption coefficient, Eo is the optical band gap, and B is constant. The absorption in this region is considered to be due to transition from the top of the extended states in the valance band to the extended states in the conduction band. 2. Exponential region. This region is supposed to be due to transitions from the

THE ROLE OF DEPOSITION RATE ON THE ELECTRICAL CONDUCTIVITY AND ENERGY GAP OF (a–Ge) THIN FILM