Research On Gan-Based Flexible LED Devices

In recent years,flexible and stretchable optoelectronic devices used in wearable and bioelectronics have received extensive attention.Flexible displays based on GaN-based high-brightness light-emitting diodes(HPLED)and micro-light-emitting diodes(Micro-LED)have become a promising research direction in the future.The miniaturization of LED chips has the advantages of high efficiency,long life and high resolution,but as the size becomes smaller,the process manufacturing and flexibility transfer become more complicated.Meanwhile,due to the self-heating effect,a large amount of heat is generated when the LED is working,which reduces the quantum efficiency and reliability of the device.Therefore,reducing the self-heating effect of LEDs has always been a difficulty for LEDs in high-brightness and integrated applications.Based on the preparation and theoretical modeling of GaN-based flexible LEDs,this thesis systematically studies the modulation characteristics of piezophototronics effect on the optical,electrical and thermal properties of the LED under bending.The main research work of this thesis consists of the following three parts:1.GaN-based LED device preparation and flexibilityInGaN/GaN MQW LEDs on silicon substrates is prepared using micro-nano processing technology,and the silicon substrate of the LEDs is thinned using deep silicon etching technology to realize the flexibility of the devices.Furthermore,the flexible transfer technology of LEDs is studied,and a flexible hydrogel substrate after LED transfer is prepared.2.Piezo-phototronics effect modulated GaN-based flexible LEDsThe influence of external stress on the self-heating effect,luminous intensity and electrical characteristics of flexible LEDs in the process of flexible bending is systematically studied,and it is proved for the first time that the piezo-phototronics effect effectively suppressed the self-heating effect.Compared with the traditional LED,when an external strain of 0.1%is applied,the luminous intensity of the LED is increased by 26.6%,and the operating temperature is reduced by 50.00% and 47.62% at the bias voltage of 6 V and 7 V,respectively.3.Theoretical model of flexible GaN-based LEDBased on the basic principles of piezo-phototronics effect,a selfconsistent coupling model is established using piezoelectric constitutive equation,Schrodinger equation,Poisson equation,and Fermi’s golden law.The influence of the external strain-induced piezoelectric potential on the generation,transmission,separation and recombination of carriers in the flexible LED is systematically discussed in this model.The physical mechanism of the optoelectronic properties of the flexible LED under the bending stress state is analyzed,and the theoretical proof of the experimental results of GaN-based flexible LEDs is given.