الفهرس 
Chapter one : IntroductionOnly 14 pages are availabe for public view
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Abstract
The purpose of this thesis is to study electric, dielectric and photo properties of Schottky devices Au/InP/Al and heterojunction cells n-CdS/p-InP. CdS powder was deposited onto p-type InP single crystal wafers to form heterojunction sample. The crystalline nature of the CdS films was verified by X-rays diffraction measurements. Gold and Aluminum contacts were deposited respectively, on the top and bottom surfaces of the samples by vacuum evaporation technique at pressures below 1.3×10-3 Pa.
Firstly, The Au/InP/Al device exhibit rectifying characteristics showing a p-n diode-like behavior for all the measuring temperatures ranging from 300 to 360 K. The current density – voltage (J-V) characteristics for the Au/InP/Al device resemble the typical dark current versus applied voltage characteristic for conventional Schottky diode. The rectification ratio of the junction was evaluated at ± 0.5V yielding a value of 140. The non-ideal J–V characteristics might indicates an intimate contact between Au and InP. The characteristic parameters of the structure such as Richardson constant, ideality factor, barrier height, built-in potential, depleting width and contact potential have been determined from the current–voltage and capacitance –voltage measurements. Under reverse bias, the conduction process was interpreted in terms of a bulk-limited transition to an electrode-limited transition, from the Poole–Frenkel effect to Schottky emission.
The Capacitance-voltage measurements, dielectric constant (ε`), dielectric loss factor (ε″) , and loss tangent tan(δ) of Al/p-InP/Au devices were measured in the frequency range 10 to 5000 kHz and temperature range 300 to 423 K. The variation of impedance Z* and dielectric constant ε* with frequency at different temperatures were plotted in the complex plan show semicircles. Ac conductivity σac(ω), of Al/p-InP/Au has been measured in the frequency range 1000 to 5000 kHz, over the temperature range 300 to 423 K, respectively. Obtained data reveal that σac(ω) obeys the relation, σac(ω) = AωS and the exponent S is found to increase by increasing temperature. The values of S of the investigated thin films lie between 0.43 ≤ S ≤ 0.83 The obtained experimental results of ac conductivity have been analyzed with reference to various theoretical models. The analysis shows that the correlated barrier-hopping (CBH) model is the dominant conduction mechanism for the charge carrier transport in the p-Inp wafers. Throughout these investigations all measurements have led to consistent interpretation of the observations.
Secondly, Heterojunction cells of n-CdS/p-InP have been fabricated by thermal evaporation of n-CdS films onto p-InP substrates. The rectification ratio of the junction was evaluated at ± 0.5V yielding a value of (90). Current density-voltage measurements (J-V) and (C-V) measurements are performed to determine the electrical properties of heterojunction cell. The forwarded current involves tunneling and is explained by a multi-tunneling capture-emission model.