Study Of Structure Modulation And Performance Improvement Of ZnO/GaN Heterojunction LED

In recent years,short-wavelength LEDs,a hot research topic in modern optoelectronics,have attracted researchers'tremendous interest because of their great application potential in both civil and military domains.The field of semiconductor material luminescence develops rapidly.ZnO,representing the 3rd generation wide-band gap semiconductors,is viewed as a very promising candidate for low-threshold ultraviolet LEDs and laser diodes owing to its intrinsic direct band gap?3.37 eV?,high exciton binding energy?60 meV?and large optical gain coefficient(10⁵ cm^-1).At present,the p-type doping problem of ZnO material is still not well solved,high quality,repeatable and stable p-ZnO is difficult to obtain,which restricts the development of its homojunction LEDs.By constructing ZnO-based heterostructure,the researchers realized the enhancement and improvement of efficiency and stability in light emitting devices.GaN belongs to the 3rd generation semiconductor luminescence materials.The doping process is mature.The structure is similar to ZnO,and the lattice mismatch is small.The n-ZnO/p-GaN heterostructure is shown to have good luminescence performance.However,n-ZnO/p-GaN heterostructure interface still has the problem of lattice mismatch and band offset,leading to weak luminescence efficiency,to further improve the efficiency and ultraviolet luminescence intensity in n-ZnO/p-GaN heterojunction LEDs has always been the goal of the researchers.Based on the preparation of high quality and the construction of n-ZnO/p-GaN heterojunction LED,with the aid of interface engineering,this paper elaborates the carrier transport and regulation at the heterostructure interface by introducing insulator Al₂O₃ layer.The n-ZnO/Al₂O₃/p-GaN heterojunction prototype LED device was constructed with introducing Ag nanowire surface plasmon?SP?.Using the surface-interface modification and Ag nanowire SP decoration,the visible and ultraviolet luminescence efficiency of the heterojunction device was improved,and the adjustable wavelength was realized.In this paper,the effects of insulator layer and Ag nanowire SP on the luminescence performance of n-ZnO/p-GaN heterostructure were studied in detail,and the physical mechanism of the luminescence enhancement and efficiency improvement was proposed.The specific content is as follows:Using atomic layer deposition?ALD?technique,high quality ZnO films were prepared on p-GaN substrate,and n-ZnO/p-GaN heterojunction prototype devices were constructed.By changing the preparation conditions of substrate temperature,cycle times and growth precursor ratio,the photoelectric properties of ZnO films were regulated.The suitable conditions for the preparation of high quality ZnO film by ALD technique were systematically studied and optimized,which offers help for the further surface-interface decoration and efficiency improvement of n-ZnO/p-GaN heterojunction devices.Based on the n-ZnO/p-GaN heterojunction prototype device,the insulator Al2O3 layer at the heterostructure interface was introduced.We studied the influence of the insulator layer thickness in heterojunction luminescence,realized effective interface regulation and carrier transport,and enhanced the ZnO ultraviolet luminescence.Moreover,the introduction of Ag nanowire SP with its resonance energy and ZnO ultravoilet emission energy matching makes ZnO excitons and Ag nanowire SP occur resonance coupling interaction.This interaction leads to the rise of ZnO internal quantum efficiency and improves heterojunction light emission efficiency.Ag nanowire decorated n-ZnO/p-GaN heterostructure LED was designed and prepared.By changing the surface density of Ag nanowire,the different coverage density of Ag nanowires will affect the luminescence performance of heterojunction.The resonance coupling effect between ZnO excitons and Ag nanowires SP results in ZnO near ultravoilet electroluminescence enhancement,and suppresses ZnO defects related to yellow-green light emission.Finally,this coupling interaction realized the wavelength adjustment effect with the emission wavelength from yellow-green region to blue-ultravoilet region.Time-resolved photoluminescencemeasurements,temperature-dependentphotoluminescenceand finite-different time-domain simulations confirmed the existence of resonance coupling between ZnO excitons and Ag nanowires SP,and the reliability of the enhanced fluorescence emission mechanism of metal SP.