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Giant UV Photoresponse of GaN-Based Photodetectors by Surface Modification Using Phenol-Functionalized Porphyrin Organic Molecules

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dc.contributor.author Rao, V. Ramgopal
dc.date.accessioned 2023-10-21T05:43:26Z
dc.date.available 2023-10-21T05:43:26Z
dc.date.issued 2019-03
dc.identifier.uri https://pubs.acs.org/doi/10.1021/acsami.8b20694
dc.identifier.uri http://dspace.bits-pilani.ac.in:8080/xmlui/handle/123456789/12570
dc.description.abstract Organic molecular monolayers (MoLs) have been used for improving the performance of various electronic device structures. In this work, the concept of organic molecular surface modification is applied for improving the performance of GaN-based metal–semiconductor–metal (MSM) ultraviolet (UV) photodetectors (PDs). Organic molecules of phenol-functionalized metallated porphyrin (hydroxyl-phenyl-zinc-tetra-phenyl-porphyrin (Zn-TPPOH)) were adsorbed on GaN, and Ni/Zn-TPPOH/GaN/Zn-TPPOH/Ni PD structures were fabricated. This process was beneficial in two ways: first, the reverse-bias dark current was reduced by 1000 times, and second, the photocurrent was enhanced by ∼100 times, in comparison to the dark and photocurrent values obtained for Ni/GaN/Ni MSM PDs, at high voltages of ±10 V. The responsivity of the devices was increased from 0.22 to 4.14 kA/W at 5 μW/cm2 optical power density at −10 V bias and at other voltages also. In addition to this, other PD parameters such as photo-to-dark current ratio and UV-to-visible rejection ratio were also enhanced. The spectral selectivity of the PDs was improved, which means that the molecularly modified devices became more responsive to UV spectral region and less responsive to visible spectral region, in comparison to bare GaN-based devices. Photoluminescence measurements, power-dependent photocurrent characteristics, and time-resolved photocurrent measurements revealed that the MoL was passivating the defect-related states on GaN. In addition, Kelvin probe force microscopy showed that the MoL was also playing with the surface charge (due to surface states) on GaN, leading to increased Schottky barrier height in dark conditions. Resultant to both these phenomena, the reverse-bias dark current was reduced for metal/MoL/GaN/MoL/metal PD structures. Further, the unusual photoconductive gain in the molecularly modified devices has been attributed to Schottky barrier lowering for UV-illuminated conditions, leading to enhanced photocurrent. en_US
dc.language.iso en en_US
dc.publisher ACS en_US
dc.subject EEE en_US
dc.subject MSM UV PDs en_US
dc.subject Photoluminescence en_US
dc.subject KPFM en_US
dc.subject Responsivity en_US
dc.subject Self-trapped holes en_US
dc.title Giant UV Photoresponse of GaN-Based Photodetectors by Surface Modification Using Phenol-Functionalized Porphyrin Organic Molecules en_US
dc.type Article en_US


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