Search query: nanostructure GaN based msm uv pd

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abstract: In this work, we report the formation of porous unintentionally doped (UID) n type GaN films under a novel alternating current (sine wave a.c. (50 Hz) photo assisted electrochemical etching (ACPEC) conditions. The formation of porous unintentionally doped (UID) n type GaN by the novel ACPEC is performed in the same electrolyte concentration (4% KOH) used in common dc constant current electrochemical etching process. Ultra violet (UV) illumination is used to assist in the generation of electron hole pairs, where etching proceeds through the oxidation and consequently, dissolution of the semiconductor surface. The ac formed UID porous GaN with excellent structural and optical properties. According to the FESEM micrographs, the GaN thin films exhibit a homogeneous nanoarchitecture of the porous structures with perfect hexagonal shape. The porous layer exhibited a substantial photoluminescence (PL) intensity enhancement with red shifted band edge PL peaks associated with the relaxation of compressive stress. The shift of E2(high) to the lower frequency in Raman spectra of the UID porous GaN films further confirms such a stress relaxation. Electrical characterizations of the MSM photodiodes were carried out by using current voltage (I V) measurements indicated that the devices were highly sensitive to ambient light
author_names: Ainorkhilah Mahmood

Zainuriah Hassan

Alhan Farhanah Abd Rahim

Rosfariza Radzali

Naser M Ahmed

Yushamdan Yusof

Mohd Haris Ridzuan Ooi Abdullah

Mohd Firdaus Roslan

Mohd Nadeem Bukhari

Sharifah Nooraishah Syed Mohd Zainol

Zaki Mohd Yusoff

Muhammad Firdaus Othman

Surani Buniran

Mohd Firdaus Roslee

Norha Abdul Hadi

Madhiyah Yahya

Siti Hajar Mohmad Salleh

Masbudi bin Baharuddin

Vicinisvarri Inderan

Kumar Sudesh
title: ENHANCING PERFORMANCE OF POROUS UNINTENTIONALLY DOPED GAN BASED MSM PHOTODETECTOR USING ALTERNATING CURRENT PHOTO ASSISTED ELECTROCHEMICAL ETCHING ACPEC TECHNIQUE
year: 2019

abstract: The present research reports the fabrication and performance evaluation of an AlGaN/GaN based metal semiconductor metal (MSM) ultraviolet (UV) photo detector on silicon (111) substrate. The MSM device has been fabricated with aluminium (Al) in an inter digitized (IDE) geometry on the molecular beam epitaxially grown epilayer. Substantially high photo current as 9.5 mA has been resulted under the illumination of 365 nm wavelength UV as compared to the dark current of 409mA with photo to dark current ratio of 23.22 and very high responsivity of 15798 A/W. Rise time as 1.01 seconds and fall time as 5.17 seconds has been observed after transient analysis of the devices. High carrier concentrations at the heterojunction due to polarization has been attributed for relatively larger photo current as compared to previous literature.
author_names: Indu Kumari

Subhashis Das

Ankush Bag
title: Selective UV Detection by AlGaN/GaN Based MSM Photo Detector for Integration with Silicon
venue: 2018 IEEE SENSORS
year: 2018

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 mW/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.
author_names: Manjari Garg

Bhera Ram Tak

V Ramgopal Rao

Rajendra Singh
title: Giant UV Photoresponse of GaN Based Photodetectors by Surface Modification Using Phenol Functionalized Porphyrin Organic Molecules.
venue: ACS applied materials interfaces
year: 2019

abstract: We report the fabrication of a GaN/sapphire ultraviolet (UV) photodetector (PD) with asymmetric (Pt Ag) and symmetric (Pt Pt) metal semiconductor metal (MSM) structure. The fabricated devices display Schottky behavior. Time dependent photoresponse analysis reveals a significant enhancement in photocurrent leading to a photoresponsivity of 37 mA/W and 267 mA/W under 13 mW optical power at 5 V bias for Pt Pt and Pt Ag devices, respectively. Further, power dependent measurements reveal a peak responsivity of 633 mA/W at 4mW optical power and 5 V bias for the Pt Ag asymmetric MSM photodetector. The significant enhancement in responsivity for asymmetric MSM UV PD is ascribed to the built in potential gradient in the GaN semiconductor, which drives a large number of charge carriers for enhanced charge collection. Further, the noise equivalent power was lowest for the Pt Ag MSM structure, which was calculated to be 4.6 x 10 14 WHz 1/2. This high performance asymmetric MSM GaN UV PD can be integrated into efficient UV PD based applications.
author_names: Shubhendra Kumar Jain

Shibin Krishna

Neha Aggarwal

Rahul Kumar

A Gundimeda

Sudhir Husale

Vinay Gupta

Govind Gupta
title: Effect of Metal Contacts on a GaN/Sapphire Based MSM Ultraviolet Photodetector
venue: Journal of Electronic Materials
year: 2018

abstract: Abstract Undoped Zinc oxide (ZnO) and Antimony doped Zinc Oxide (Sb: ZnO) nanostructures (nanocones and nanoflakes) with different doping concentrations of Sb (3 at% 6 at% and 9 at% were grown on flexible (ITO/PET) substrate using a simple hydrothermal method. The seed layer of ZnO was prepared using sol gel method, which was then used as the base to grow Sb: ZnO nanostructures by hydrothermal method. Structural, optical and electrical characteristics of undoped and Sb: ZnO nanostructures were studied for three different doping concentrations of Sb. The structural and morphological studies of the prepared samples were carried out using XRD and FESEM. EDAX was used for elemental analysis. The XRD spectrum reveals ZnO wurtzite structures. The FESEM results clearly indicate that there was no change in morphology of ZnO nanostructures with the substitution of Sb in ZnO lattices. The optical studies were performed on all samples using UV Vis spectroscopy. It was observed that the transmission and the bandgap energy reduced with an increase in doping concentration. IV curves were plotted using an impedance analyzer. The samples were studied under dark conditions and under UV light of 365 nm. A monotonic increase in electrical conductivity was observed with increase in doping concentration, asserting the fact that addition of Sb to ZnO increases the conductivity of the samples, making Sb: ZnO a good candidate for photodetection. The responsivity and efficiency of the device under UV illumination of 365 nm were found to be 2.62 A/W and 893.35% respectively, with the highest values being observed for 9 at% of Sb doping.
author_names: Nazia Fathima

Natarajan Pradeep

Jyothi Balakrishnan
title: Enhanced optical and electrical properties of antimony doped ZnO nanostructures based MSM UV photodetector fabricated on a flexible substrate
venue: Materials Science in Semiconductor Processing
year: 2019

abstract: Abstract In this study, the fabrication and structural characterization of Antimony (Sb) doped Zinc Oxide (ZnO) based interdigitated Metal Semiconductor Metal (MSM) Ultraviolet (UV) photodetectors are reported. Sb doped p ZnO nanostructures were grown using the sol gel and hydrothermal methods on flexible ITO/PET substrates. Aluminium (Al) interdigitated contacts of thickness 20 nm, were deposited using the thermal evaporation technique to realise planar MSM structures. The structural morphology and element analysis of the as prepared samples were studied using XRD, FESEM and EDS methods. At an applied magnetic field of 1 T, the Hall measurements revealed that the device had a resistivity of 2.0697 x 10 3 O*cm, a hole mobility of 1922 m2/(V*s) and hole concentration of 0.1571 x 1019 cm 3. The optoelectrical characterization (without and with 365 nm of UV light) was performed on the MSM photodetectors with different finger electrode spacing i.e. gap sizes (0.1 cm, 0.2 cm and 0.3 cm) The results show that the device with finger spacing of 0.1 cm exhibited the maximum photocurrent. The responsivity and external quantum efficiency were calculated as 3.797 A/W and 1292% respectively. The flexible device was subjected to mechanical stress, and the dark current and photocurrent were measured for various bending/ convex arc angles (29.980, 48.720, 64.960 and 97.450) It was observed that the dark current and photocurrent reduce with the increase in bending angles. The current values were reproducible even with repeated flexing and relaxing of the device. This proved that the adhesion of the active layer of Sb doped p ZnO to the ITO/PET substrate is good, which makes it a good device.
author_names: Nazia Fathima

Natarajan Pradeep

Jyothi Balakrishnan
title: Investigations of the effects of electrode geometry and mechanical stress on Antimony doped Zinc Oxide nanostructures based MSM UV photodetectors fabricated on flexible substrates
venue: Solar Energy Materials and Solar Cells
year: 2019

abstract: Abstract This work reports the ultraviolet (UV) detection characteristics of zinc oxide (ZnO) nanorods (NR's) based metal semiconductor metal (MSM) devices. ZnO NR's were grown on silicon (Si) substrates (p type) by low temperature hydrothermal method in two steps. In the first step, approximately 50 nm thick pure ZnO seed layer was grown on Si, then in the second step, main growth of ZnO NR's were done above seed layer. The structural morphology of ZnO NR's were investigated by atomic force microscope (AFM) and by cross sectional scanning electron microscopy (X SEM) respectively. The results showed that high density NR's were grown uniformly above the ZnO seed layer and the tip of NR's were found in the shape of a hexagonal. After the growth of ZnO NR's, interdigited palladium (Pd) electrodes were deposited by using shadow mask technique. The electrical characterization of the Pd/ZnO NR's/Pd based detectors was studied under UV light. The values of contrast ratio and responsivity were calculated from I V characteristics of MSM UV detectors. These results may be helpful for the simplistic fabrication of hydrothermally grown ZnO NR's based UV detectors.
author_names: Shaivalini Singh

Si-Hyun Park
title: Fabrication and properties of ZnO nanorods based MSM UV detectors on silicon substrates
year: 2017

author_names: Shuang Liang

W Cai

Yan Li

Yaoxing Liu

Yicheng Lu

Chuong Anh Tran

Robert Frank Karlicek

Ian T Ferguson
title: GaN based MSM UV photodetectors
year: 1996

abstract: Abstract We report the fabrication and UV sensing properties of tower like GaN nanostructures. Material properties of GaN have been characterized by X ray diffractometer, transmission electron microscopy, and micro Raman and photoluminescence (PL) analysis. Temperature dependent PL measurement proves the strong band edge emission and negligible yellow emission band of the tower like GaN, which signifies the high crystal quality of GaN. The optimized UV photodetector in MSM structure based on the tower like GaN shows a response current of 52 mA and a responsivity of 122.07 mA/W at 3 V bias. Furthermore, the fast UV response of the device exhibits less than 82 ms rise time and 164 ms decay time, respectively. The work indicates a promising quality of GaN nanostructure by simple and economic CVD route and its potential application in UV light sensing devices.
author_names: Ting Wang

Fa Cao

Xiaohong Ji

Qinyuan Zhang
title: Study on tower like GaN nanostructure: Growth, optical and fast UV sensing properties
venue: Superlattices and Microstructures
year: 2019

abstract: A model of currents in GaN based metal semiconductor metal(MSM) UV photodetectors have been obtained in one dimensional structure using steady state continuity equations,including the effect of surface states.According to the model,the photocurrent gain is explained,and the influences of the width of depletion regions on the photocurrents as a function of the applied bias voltage are investigated.The saturation bias voltage of 6V,stable current of 6x10~ 8) A and responsivity of 0.0857A/W are experimentally obtained.These results are in good agreement with the experimental ones.
author_names: Yang Mo-hua
title: Photo response in GaN based MSM UV Detectors
year: 2006