A Study On The Reliability Of GaN/Si LEDs

Recently,growth of GaN on Si substrate has made great progress,it is reported that high power GaN/Si LED have been fabricated.It is known that the reliability of devices is connected to commercial value and manufactory of an technology,so study on properties of GaN/Si LED is far from important.But as a brand-new product, study and analysis on GaN/Si LED is still needed.In this dissertation,photoelectric and electrostatic discharge properties of GaN based LED chips on Si substrate after aging at high direct current are studied.Some significant and innovative results achieved are following:1.Accelerated aging experiment was carried for LED chips of 200μm×200μm and high power LED chips at high direct current respectively.The results show that 500mA test current in 5min and 1A test current in 15min are the proper test condition, and the results of large current accelerated aging experiment are matched well with ordinary test current.2.GaN/Si LED chips were stroke by human being mode(HBM) and machine mode(MM) electrostatic discharge,results show that the effect of ESD of 200V MM is close to ESD of 1200V HBM,while the effect of the former is shaper,so HBM is commonly chosen in ESD experiment.Different ESD voltage doesn't influence the accelerated age experiment in HBM.3.High power blue GaN/Si LED chips(400μm×600μm) with and without reflector were stroke by 1200V(HBM) and the pass rate of the two are closed which show that Ag reflector can raise the light output and have no influence on the ESD.4.Study was carried on optical and electrical characterization of high power green LED on Si(111) substrate by MOCVD with chip dimension of 400μm×600μm in our laboratory.The forward bias of the LED with Ag reflector is about 3.59 V under 20 mA,the light output power is about 7.3 mW with dominant wavelength of 518 nm,the light output power achieves 28.2mW under 90mA,the light output efficiency is 7.5%,the saturate output current was as high as 600mA.The light degradation of LED with Ag reflector was smaller than LED without Ag reflector after 216 hours accelerate aging test under 200mA,this phenomenon was induced by Ag reflector,which can raise the light extraction efficiency and lower the temperature of the chip itself.The results of above all have already been applied in LED test of Lattice Power (Jiang Xi) Corporation.This work is supported by 863-project of China and electronic development program in China.