A Study Of GaN-based UV-LED Multi-quantum Wells Structure Optimization

In recent years, Ga N-based UV-LED has become a hot topic of the whole society owning to its good performances. Due to their advantages such as small volume, long life more than 100 times, environment friendly and low-voltage power supply, etc., Ga N-based UV-LED have been widely used in the development of white LED and have been a new generation UV light source to replace mercury lamps. However, the current luminous efficiency of Ga N-based UV-LED is still low, the luminous performance can not meet the needs of the whole society. Therefore, it is necessary to develop Ga N-based UV-LED with better optoelectronic performance. The purpose of this paper is to improve the luminous efficiency of Ga N-based UV-LED. First of all, the research progress of Ga N-based quantum well structure LED is presented in this thesis. Secondly, the main problems of Ga N multi-quantum well structure LED have been analyzed from different aspects, and a detailed study has been made on how to improve the brightness of Ga N multi-quantum well structure LED through effective measures. Finally, this paper is mainly concerned with the effect of the increased well width and indium flux in the well layer on Ga N-based LED’sluminous efficiency, the main work done are outlined as follows:1. This paper gives a detailed analysis of the effect of different growth time in quantum well layers on the crystalline quality, MQWs’ interface characteristics, PL and EL spectra characteristic. Theoretical analysis results show that the stress in c-plane was increased effectively with the increase of well width, less defects were produced in the process of forming three-dimensional islands;On the other hand, the increase of well width would limit more carriers in well layer, there will be more electrons and holes occur radiative recombination in well layers. These two aspects play an active role in increasing Ga N-based LED’s luminous efficiency.2. This paper studied the effect of different indium-doped in quantum well layers on the Ga N-based UV-LED. The polarization charge density between well layers and barrier layers was calculated theoretically, the optical and electrical properties and crystalline quality was analized in detail at the same time. The results showed that a better optoelectronic properties of LED can be obtained when indium-doped in the well layers is15%. With the increase of indium flux, the localized effect of indium atoms was enhanced and exceeded the effect of dislocation density caused by the more indium-doped in the light-emitting process. However, when indium-doped in the well layers is 25%, indium-doped can result in a greater lattice mismatch, leading to worse crystalline quality and optoelectronic performance of Ga N-based LED.The final results show that the optoelectronic performance of Ga N-based ultraviolet LED has been improved. A wavelength about 376 nm Ga N-based LED has been obtained with the forward voltage of 3.85 V and the LOP of 86.39 m W at the forward current of 350 m A.