GaN Nanotowers Grown on Si (111) and Functionalized with Au Nanoparticles and ZnO Nanorods for Highly Responsive UV Photodetectors

Abstract

Vertically aligned GaN nanotowers (NTs) were grown on the Si (111) substrate by plasma-assisted molecular beam epitaxy to design a highly responsive ultraviolet (UV) photodetector. The UV detector fabricated on a bare GaN-NT array yielded highly sensitive and repeatable device characteristics attributed by high responsivity (R), low noise equivalent power (NEP), and a high external quantum efficiency (EQE) of 484.77 A/W, 1.76 × 10 −13 W.Hz -1/2 , and 1.85 × 10 5 %, respectively. Furthermore, the developed UV photodetector demonstrated fast response with excellent stability when functionalized with Au nanoparticles and ZnO nanorods. This hybridized GaN-NT-based device with ZnO nanorods and Au nanoparticles significantly accelerated the performance of the device where a prominent threeorder reduction under dark current is observed along with gigantic R, lower NEP, and an extremely enhanced EQE of 7042 A/W, 1.84 × 10 −14 W.Hz -1/2 , and 2.7 × 10 6 %, respectively. The mechanism elaborating the enhanced device performance with a localized surface plasmon effect has been discussed through an energy band diagram. The fabricated highly sensitive device can lead the path toward future optoelectronic applications of integrated III-nitride technology.

Fabrication of GaN Nano-towers Based Self-powered UV Photodetector

“…The distribution density of grown NTs is calculated to be 3.5× 10 10 cm -2 . It was also observed that the high quality AlN buffer layer grown at higher substrate temperature (800 o C) resulted in better structural and morphological properties in comparison to the structure grown at AlN buffer grown at lower substrate temperature [19,20] Besides this, the increment in surface area is evaluated in concurrence with FESEM & AFM measurements which confirm the enhancement from 9 µm 2 to 15.6 µm 2 from planar to tapper ended GaN-NTs morphology. The grown GaN-NTs with enhanced surface area consequently allow more photon absorption sites to generate a large number of photo-excited electron-hole pairs (EHPs).…”

“…The responsivity value of 35.4 A/W is significantly higher as compared to other bare GaN-based UV-PD as tabulated in Table 1. However, the recently reported GaN-NT based UV-PD [19] demonstrated higher responsivity of 88.6 A/W at -3V, moreover the performance of the devices is limited to photo-conductive mode only with ~300x higher response time. In addition, the present analysis reports optimised AlN buffer with reduced defect density in GaN-NTs.…”

“…Recently, it has been reported that GaN-nanocolumnar structure can offers wavelength tunability, low dislocation density and lower lattice related strain and very good response. [14][15][16] However, the fabricated devices are non-operational in photovoltaic mode i.e. zero applied bias and display very high response time.…”

Fabrication of GaN nano-towers based self-powered UV photodetector

“…The distribution density of grown NTs is calculated to be 3.5 × 10 10 cm −2 . It was also observed that the high quality AlN buffer layer grown at higher substrate temperature (800 °C) has resulted in better structural and morphological properties in comparison to the heterostructure grown with a lower substrate temperature of AlN buffer layer 15 , 23 . Besides this, the increment in surface area is evaluated in concurrence with FESEM&AFM measurements which confirms the enhancement from 9 to 15.6 µm 2 from planar to taper-ended GaN-NTs morphology.…”

Enhanced performance of ZnO nanorod array/CuSCN ultraviolet photodetectors with functionalized graphene layers

“…This hole-trapping mechanism through oxygen adsorption and desorption in ZnO NRs augments the high density of trap states usually found in NRs due to the dangling bonds at the surface and thus enhances the NW photoresponse. 8,14,15 However, a high bias voltage must be applied in order to obtain a high responsivity, which results in a long response time. ZnO-based p-n photodiodes have the advantages of fast response times, no applied elds, and no oxygen dependency.…”