Abstract
The incorporation of doping elements in ZnO nanostructures plays an important role in adjusting the optical and electrical properties in optoelectronic devices. In the present study, we fabricated 1-D ZnO nanorods (NRs) doped with different In contents (0% ~ 5%) on p-GaN films using a facile hydrothermal method, and investigated the effect of the In doping on the morphology and electronic structure of the NRs and the electrical and optical performances of the n-ZnO NRs/p-GaN heterojunction light emitting diodes (LEDs). As the In content increased, the size (diameter and length) of the NRs increased, and the electrical performance of the LEDs improved. From the electroluminescence (EL) spectra, it was found that the broad green-yellow-orange emission band significantly increased with increasing In content due to the increased defect states (oxygen vacancies) in the ZnO NRs, and consequently, the superposition of the emission bands centered at 415 nm and 570 nm led to the generation of white-light. These results suggest that In doping is an effective way to tailor the morphology and the optical, electronic, and electrical properties of ZnO NRs, as well as the EL emission property of heterojunction LEDs.
Highlights
ZnO, which possesses a wide band-gap (3.37 eV) and a high exciton-binding energy (60 meV), is a promising n-type semiconducting material in optoelectronic devices such as solar cells, laser diodes (LDs), and light emitting diodes (LEDs)[1,2,3,4]
Many studies have been conducted to incorporate In into ZnO NRs using various synthesis methods, and In-doped ZnO NRs have been applied to practical applications of optoelectronic devices[22,23,24,25,26]
We fabricated n-ZnO NRs/p-GaN heterojunctions using a facile hydrothermal method, in which In was doped into the ZnO NRs to improve the electrical conductivity and to tune the optical band-gap energy, and the LED performances were examined by varying the In content
Summary
ZnO, which possesses a wide band-gap (3.37 eV) and a high exciton-binding energy (60 meV), is a promising n-type semiconducting material in optoelectronic devices such as solar cells, laser diodes (LDs), and light emitting diodes (LEDs)[1,2,3,4]. The emission efficiency and output power of the n-ZnO NRs/p-GaN heterojunction LEDs are insufficient to achieve high performance devices due to their lower carrier injection efficiency, resulting from a high energy barrier at the junction interface (type-II band alignment: staggered heterojunction)[15] This problem can be overcome by the incorporation of foreign elements in the ZnO NRs such as Al, Ga, In, Cl, Sn, Cu, and Br, etc., which can change the crystallinity, geometry (including size and morphology) and electronic property of the NRs, thereby enhancing the electrical and optical properties of the LEDs. The incorporated doping elements enable the tuning of the light emissions of the LEDs. Studies on color-tuning have recently become prominent because of the growing demand for white-LEDs which have many advantages over traditional single light LEDs, such as lower energy consumption and higher transfer efficiency[16,17,18]. This work provides an effective path for developing nanostructure-based devices for color-tunable LEDs
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