Improvement the efficacy of Al/CuPc/n-Si/Al Schottky diode based on strong light absorption and high photocarriers response
Elsayed Elgazzar
Abstract
Abstract Copper phthalocyanine has been prepared by simple chemical approach and its structural and optical properties were investigated. X-ray diffraction pattern exhibits a notable peak at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mi>θ</mml:mi> <mml:mo>=</mml:mo> <mml:mn>6.75</mml:mn> <mml:mo>°</mml:mo> </mml:math> assigned to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>−</mml:mo> <mml:mspace width=".25em"/> </mml:math> phase of CuPc. SEM images show the particles distributed in nanospheres with average size at about 50 nm. The linear optical constants like optical band gap <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> and dielectric constants ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ε</mml:mi> <mml:mo accent="false">′</mml:mo> <mml:mo>,</mml:mo> <mml:mi>ε</mml:mi> <mml:mo accent="false">″</mml:mo> </mml:math> ) were estimated from transmittance and reflectance spectra in the wavelength range from 250 to 900 nm. The energy gap was found to be 1.62 and 2.90 eV dependent on the incident photon energy. Al/CuPc/n-Si/Al Schottky diode has been fabricated using thermal evaporation technique. The electronic parameters such as the ideality factor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:mi>n</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>,</mml:mo> </mml:math> series resistance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> <mml:mspace width=".25em"/> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mo>,</mml:mo> </mml:math> and barrier height ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) were evaluated in dark by applying the ( I – V ), Cheung-Chung, and Norde models. At various illumination intensities, the photocurrent sensitivity was studied based on the response of trapped charge carriers. At 1 Mhz, the built-in voltage <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> <mml:mi>i</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> and donor concentration <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> were calculated from ( C – V ) measurements. The findings revealed that CuPc/n-type Si can be used as photodiode in optoelectronic applications.