Abstract-The fabrication and characterization of a Si/ZnO thin film heterojunction ultraviolet photodiode has been presented in this paper. ZnO thin film of ~100 nm thick was deposited on <100> Silicon (Si) wafer by atomic layer deposition (ALD) technique. The Photoluminescence spectroscopy confirms that as-deposited ZnO thin film has excellent visible-blind UV response with almost no defects in the visible region. The room temperature current-voltage characteristics of the n-ZnO thin film/p-Si photodiodes are measured under an UV illumination of 650 µW at 365 nm in the applied voltage range of ±2V. The current-voltage characteristics demonstrate an excellent UV photoresponse of the device in its reverse bias operation with a contrast ratio of ~ 1115 and responsivity of ~0.075 A/W at 2 V reverse bias voltage.
This paper represents the electrical and optical characteristics of a SiNW/ZnO heterojunction diode and subsequent studies on the photodetection properties of the diode in the ultraviolet (UV) wavelength region. In this work, silicon nanowire arrays were prepared on p-type (100)-oriented Si substrate by an electroless metal deposition and etching method with the help of ultrasonication. After that, catalyst-free deposition of zinc oxide (ZnO) nanowires on a silicon nanowire (SiNW) array substrate was done by utilizing a simple and cost-effective thermal evaporation technique without using a buffer layer. The SEM and XRD techniques are used to show the quality of the as-grown ZnO nanowire film. The junction properties of the diode are evaluated by measuring current-voltage and capacitance-voltage characteristics. The diode has a well-defined rectifying behavior with a rectification ratio of 190 at ˙2 V, turn-on voltage of 0.5 V, and barrier height is 0.727 eV at room temperature under dark conditions. The photodetection parameters of the diode are investigated in the bias voltage range of ˙2 V. The diode shows responsivity of 0.8 A/W at a bias voltage of 2 V under UV illumination (wavelength D 365 nm). The characteristics of the device indicate that it can be used for UV detection applications in nano-optoelectronic and photonic devices.
In this paper, fabrication and characterization of a sol-gel derived n-ZnO nanoparticle/p-Si heterojunction diode has been presented. A strong diffraction peak (002) obtained from XRD spectra of sol-gel derived ZnO thin film indicates that the growth of hexagonal wurtzite ZnO nanoparticles are preferably along the c-axis. The surface morphological features extracted from AFM and SEM images predict the uniform growth of ZnO nanoparticles over the p-Si substrate. The optical properties of ZnO nanoparticles have been measured in the spectral range of 300-1000 nm using ellipsometer and photoluminescence spectroscopy. The optical transmittance of ZnO nanoparticles has been observed between 81 and 92.66 % in visible region and the optical band gap has been found out to be 3.24 eV. Finally, metallic contacts were deposited on top of ZnO layer and bottom of Si layer to perform electrical characterization of nanostructured n-ZnO/p-Si heterojunction diodes. Electrical parameters including reverse saturation current, ideality factor, barrier height, rectification ratio have been calculated to explore the potential of the device for futuristic nanoelectronic and optoelectronic device applications.
Articles you may be interested inImpact of annealing on the chemical structure and morphology of the thin-film CdTe/ZnO interface J. Appl. Phys. 116, 024312 (2014); 10.1063/1.4890235 CdS nanofilms: Effect of film thickness on morphology and optical band gap Growth morphology and electrical/optical properties of Al-doped ZnO thin films grown by atomic layer deposition J. Vac. Sci. Technol. A 30, 021202 (2012); 10.1116/1.3687939Texture vs morphology in ZnO nano-rods: On the x-ray diffraction characterization of electrochemically grown samplesIn this paper, the authors have investigated the structural, optical, and electrical characteristics of silicon nanowire (SiNW)/zinc oxide (ZnO) core-shell nanostructure heterojunctions and compared their characteristics with Si/ZnO planar heterojunctions to investigate the effect of surface morphology of Si substrate in the characteristics of Si/ZnO heterojunction devices. In this work, ZnO thin film was conformally deposited on both p-type h100i planar Si substrate and substrate with vertically aligned SiNW arrays by atomic layer deposition (ALD) method. The x-ray diffraction spectra show that the crystalline structures of Si/ZnO heterojunctions are having (101) preferred orientation, whereas vertically oriented SiNW/ZnO core-shell heterojunctions are having (002)-oriented wurtzite crystalline structures. The photoluminescence (PL) spectra of Si/ZnO heterojunctions show a very sharp single peak at 377 nm, corresponding to the bandgap of ZnO material with no other defect peaks in visible region; hence, these devices can have applications only in UV region. On the other hand, SiNW/ZnO heterojunctions are having band-edge peak at 378 nm along with a broad emission band, spreading almost throughout the entire visible region with a peak around 550 nm. Therefore, ALD-grown SiNW/ZnO heterojunctions can emit green and red light simultaneously. Reflectivity measurement of the heterojunctions further confirms the enhancement of visible region peak in the PL spectra of SiNW/ZnO heterojunctions, as the surface of the SiNW/ ZnO heterojunctions exhibits extremely low reflectance (<3%) in the visible wavelength region compared to Si/ZnO heterojunctions (>20%). The current-voltage characteristics of both Si/ZnO and SiNW/ZnO heterojunctions are measured with large area ohmic contacts on top and bottom of the structure to compare the electrical characteristics of the devices. Due to large surface to-volume ratio of SiNW/ZnO core-shell heterojunction devices, the output current rating is about 130 times larger compared to their planar version at 2 V forward bias voltage. This higher output current rating can be exploited for fabricating high-performance nanoelectronic and optoelectronic devices in near future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.