Structural, Electrical, and Photodetection Characterization of a Pentacene Interdigitated MSM Photodiode

This work reports the fabrication and characterization of p-type organic metal-semiconductor-metal (MSM) Schottky barrier visible photodetector. The photodetector structure is interdigitated planar Al/pentacene/Al. Pentacene thin films were deposited by thermal vacuum deposition technique on an n-Si <111> substrate. The x-ray diffraction (XRD) measurement showed that the pentacene thin film exhibited a polycrystalline triclinic (anorthic) nature. The film's morphology was examined by scanning electron microscopy (SEM) which showed vertically aligned nanograins and distinct boundaries. Pentacene chemical analysis was performed using energy-dispersive x-rays (EDX). The optical properties of pentacene were studied by UV-visible (UV-VIS) absorbance spectra. The photodetector parameters were extracted from current-voltage (I-V) curves at room temperature under dark and illuminated conditions for applied voltages from - 4 V to 4 V and optical power ranging from 4 mu w to 86.5 mu w at 620 nm. The device's dark environment parameters have been analyzed by conventional thermionic theory and Cheung's functions. These parameters are compared with contrasts such as saturation current, barrier height, and ideality factor. The estimated photodetection parameters include responsivity (3.37 A/W), detectivity (5.59 x 10(8) mHz(1/2)W(-1)), and sensitivity (4.65), and the device exhibited an external quantum efficiency of more than 1 (675%). The capacitance-voltage (C-V) characteristics at different frequencies were also examined. The doping concentration, space charge width, the built-in voltage, barrier height, and maximum electric field were extracted from the C-V measurements. The results of the study reveal that the Al/pentacene/Al organic MSM contact fabricated by a simple vacuum thermal deposition technique can be used as a substitute for inorganic visible photodiode applications.

Automated summary

This work presents the fabrication and characterization of a p-type organic metal-semiconductor-metal (MSM) Schottky barrier visible photodetector. The pentacene thin film was deposited on an n-Si <111> substrate using thermal vacuum deposition. The properties and performance of the photodetector were analyzed, and the results showed that the fabricated organic MSM contact has potential applications in visible photodiode devices.