Study On The Numerical Simulation Of V-pit Hole Injection In GaN-based Green LED

Multi-primary synthetic white LED has the advantages of no need for phosphor,high luminous efficiency,good color rendering and long life.This white light illumination is the future development direction of high-quality full-spectrum LED.However,so far,the luminous efficiency of green and yellow LEDs is still relatively low compared to blue and red LEDs.Therefore,it is extremely important to improve the luminescent properties of GaN-based green LEDs and to obtain efficient green LEDs.Since the V-pit can promote the injection of holes,the hole injection efficiency of the GaN-based green LED can be improved.Therefore,the V-pit hole injection in the GaN-based green LED is the main research object.At the same time,it is considered that the numerical simulation method not only has the advantages of saving scientific research funds and time,but also can make up for the shortcomings of observing some microscopic physical quantities in experiments.Therefore,numerical simulation is used as a research method.Firstly,this paper briefly describes the use of the semiconductor device simulation software Silvaco TCAD,as well as the basic equations and models of numerical simulation.Then,some important parameters in the numerical model are changed,and the numerical simulation results are compared.The influence of these parameters on the numerical simulation results is analyzed.The detailed results are shown in Chapter 3.These findings can speed up the construction of numerical models and shorten the time to match the experiment.On this basis,the numerical model of GaN-based green LED is constructed,and the V-pit hole injection is studied.The main results are as follows:It is concluded that the V-pits only play a supporting role in the whole hole injection when the V-pit area ratio is less than 10%,and the relationship between the V-pit injection ratio and the V-pit area ratio and the hole current density is found.By changing the temperature and the number of cycles of superlattice growth,three samples with different V-pit area ratios were obtained.As the proportion of V-pit area increased,the forward voltage decreased in turn,and EQE increased in turn.The numerical model is established.The theoretically calculated EQE and I-V curves are matched with the experimental trend.Using this model,it is found that the V-pit changes the distribution of hole current,and the hole current density increases significantly at the V-pit.cut back.Further analysis found that the current density increased from 5A/cm² to 35A/cm².In the experiment,the V-pit hole injection of the three samples only played an auxiliary role;and the V-pit hole current ratio increased linearly with the V-pit area ratio.And the slope of this linear relationship is independent of current density.It is also found that as the current density increases,the V-pit hole current ratio decreases;and the larger the current density,the smaller the decrease in the V-pit hole current ratio.It is stated that the GaN hole blocking layer?GaN HBLP?of the P region can increase the V-hole hole current ratio,but it will increase the electron leakage in the platform region,thereby reducing the IQE.The Al_0.5Ga_0.5N hole blocking layer(Al_0.5Ga_0.5N HBLP)in the P region can effectively slow the electron leakage of the platform,but it will force electrons to flow into the V pit,thereby increasing the electron leakage of the V pit.Although Al_0.5Ga_0.5N HBLP is improved compared to GaN HBLP IQE,it is still lower than the basic model.The Al_0.5Ga_0.5N hole blocking layer(Al_0.5Ga_0.5N HBLN)in the N region not only can alleviate the electron leakage from the V pit,but more importantly,can reduce the hole leakage of the V pit and force the hole to turn.Entering the first quantum well increases the radiation recombination rate in the quantum well.Eventually,IQE is improved and the forward voltage is increased.