Study On The Effect Of Structure And Growth Method Of Quantum Barrier On The Performance Of GaN-based Long Wavelength LED On Si Substrate

Over the past decades,due to the low efficiency of yellow-green band LED,semiconductor lighting technology can only be achieved by blue-light LED exciting yellow phosphor.With the continuous improvement of the light efficiency of blue LED,the semiconductor lighting technology of blue LED exciting yellow phosphor has become the mainstream of the market and has made an important contribution to global energy saving and emission reduction.Although the fluorescent LED lighting technology has high light efficiency,its light quality is not high enough.Which is mainly manifested in the color rendering index,the difficulty of coordinated development between color temperature and light efficiency,and the potential"blue light hazard"risk.However,neither the InGaN material system nor the AlGaInP material system can achieve higher luminous efficiency in the yellow-green band,which is also the difficulty of multi-primary color synthesis of white LED technology.In this paper,based on the previous research work of yellow-green LED with high light efficiency,the influence of quantum barrier structure and growth method on the photoelectric performance of long-wavelength LED is studied in order to further improve the luminous efficiency of yellow-green LED.The following research results have been achieved:1.By introducing different amounts of H₂ into the growth process of GaN quantum barrier,the effects of H₂ on the interface and photoelectric properties of green LED MQW barrier were studied.It is found that introducing H₂ into GaN barrier growth process can effectively eliminate In-rich clusters at InGaN/GaN interface and improve the crystal quality of active region.At 20 A cm^-2 current density,the external quantum efficiency?EQE?of LED devices with 1 L hydrogen in the growth process of quantum barrier is 28.31%,which is much higher than that of LED devices without hydrogen in GaN barrier?EQE 14.79%?.However,the amount of H₂ introduced should not be too large.Excessive H₂ will reduce the quality of the well/barrier interface,weaken its carrier limitation ability and aggravate the droop effect of current.2.By adjusting Al component of EBL,the effect of Al component on hole injection path and luminous efficiency of LED devices is explored.It is found that the effect of Al component on luminescence efficiency is mainly manifested in two aspects:one is that the increase of Al component is beneficial to the injection of holes from the V-shaped pit sidewall into the active region of multi-quantum wells;the other is that the increase of Al component also reduces the quality of p-type GaN crystals,resulting in a decrease in the concentration of holes.When the current density is 20 A cm^-2,the EQE of the three samples with Al content of 20%,50% and 80% are 41.13%,43.74% and 25.52%,respectively.Therefore,the hole injection efficiency and crystal quality should be taken into account in the final barrier design in order to obtain the best optoelectronic performance.3.The influence of the number of Si doped quantum barriers on the luminescent properties of GaN-based yellow LED was studied.The results show that the number of Si doped quantum barriers increases from 6 to 8,GaN barriers tend to grow in 2D,the average thickness of MQW barriers becomes thinner,and QCSE decreases.It is also found that with the increase of the number of Si doped quantum barriers,the holes are mainly concentrated in the quantum wells near the P side,and the matching degree of electrons and holes in the active region decreases,while the EQEmax decreases.When the current density is 20 A cm^-2,the EQE of three samples doped with 6,7 and 8 Si quantum barriers are 19.06%,18.86% and 17.70% respectively.Although the EQE of long-wavelength LEDs has made great progress,the EQE of long-wavelength LEDs is still lower than that of blue light LEDs.As an important part of the multi-quantum well active region,the quantum barrier not only relates to the overall crystal quality of the active region,but also regulates the injection of holes from the sidewall of the V-shaped pit and suppresses electron leakage by changing the doping and structure.Therefore,the subsequent research on the direction of the quantum barrier should further improve the EQE of the long-wavelength LED based on how to ensure and improve the quality of the active region,how to improve the hole sidewall injection and suppress the electron leakage angle of the V-shaped pit.