Study Of Quantum Barriers In The GaN-based Light Emitting Diodes

Light-emitting diode(LE D)based on G allium Nitride(G aN)is widely used in solid-state lighting,liquid crystal display backlight,color display,and automotive LE D.A t present,the main problem of G aN-based LE D s is the efficiency droop at high current density.A s to the cause of the efficiency droop,the industry has not reached a unified conclusion.T he quantum-confined S tark effect induced by polarized charges,carrier leakage,and A uger recombination are all thought to be possible causes of their efficiency droop,the injection efficiency and distribution uniformity of carriers(especially holes)are also considered to be the most likely causes of efficiency droop.In this paper,LED s with different barrier structures are designed to improve the carrier injection efficiency and uniformity,suppress the efficiency droop,and improve the device performance.The main work of this paper is as follows:1.A structure with a barrier with gradient thickness is designed,which is characterized in that the barrier thickness decreases uniformly along the growth direction with a fixed value,and performance was improved.This is mainly because:with the decrease of the barrier thickness near the p-side,the injection efficiency of the carriers and the uniformity of the hole distribution are improved,and the radiation recombination rate of the carriers is increased,finally,the optical output power of the device is increased.2.0 n the basis of the above,a new barrier structure with sub-area variation in thickness is further designed,the characteristic of this structure is that the three barriers near the n-type region and the three barriers near the p-type region maintain the same thickness respectively.It is found that with the decrease of the three barrier thicknesses near the p-type region,the efficiency droop is gradually suppressed and the device performance is improved.T his is because the increasing thickness of the three barriers near the n-type region and the thinning of the three barriers near the p-type region lead to an increase in the efficiency of carrier(especially hole)injection,so there are more holes and electrons in the quantum well for radiative recombination.3.A n InG aN/G aN/InG aN triangular barrier structure is designed to reduce the lattice mismatch between the barrier and the quantum well.C ompared with the traditional G aN barrier and InG aN barrier structures,the LE D with this barrier structure has higher output power and lower efficiency droop.Further research shows that compared with G aN barrier structure,the LE D with triangular barrier structure has better carrier injection efficiency and hole distribution uniformity.In addition,compared with the InG aN barrier structure,the carrier distribution uniformity of LED with triangular barriers is slightly lower,but the carrier injection efficiency is improved significantly.It is shown that both the carrier distribution uniformity and the carrier injection efficiency affect the efficiency droop of GaN-based LEDs.