Growth Regulation And Optical Properties Of InGaN/GaN Micro-Arrays

GaN based light-emitting diodes(LED)have been widely used in the field of lighting and display due to energy conservation and environmental protection.However,commercial LED epitaxial materials with thin film structure have the problems of single emission wavelength,high dislocation density,strong polarization electric field and low light extraction rate.The related reports show that GaN based micro/nano arrays structure can solve the above problems well.Therefore,it is important to study the growth process and optical properties of InGaN/GaN micro-arrays structure for commercial development of new LED epitaxial structures with high performance.The effect of the growth process on the morphology and optical properties of the InGaN/GaN micro-arrays structure was systematically studied by using the metal organic chemical vapor deposition technique and the selective area secondary epitaxial growth method.The effect of the multiple quantum well(MQWs)growth process on the InGaN/GaN platelet micro-arrays structure was analyzed.The main research contents are as follows:(1)Controllable growth of tablet,platelet and pyramid GaN micro-arrays structure.After that,5 cycles InGaN/GaN MQWs continued to growth.Scanning electron microscopy(SEM)and atomic force microscopy(AFM)characterization results indicate that the arrays morphology changes after growth InGaN/GaN MQWs.The photoluminescence(PL)results show that the spectra of InGaN/GaN micro-arrays structures with different morphologies are composed of multiple luminescence peaks,and the arrays morphology directly affects its luminescence properties.The results of cathodoluminescence(CL)show that the luminescence wavelengths of(0001)c facet and(1011)seni-polar facets in InGaN/GaN platelet micro-arrays structure are obviously different.This is mainly caused by the different In contents in the MQWs of different facets.The microstructure of InGaN/GaN platelet micro-arrays was characterized by high-resolution transmission electron microscopy(HRTEM)and the growth mechanism and luminescence properties were analyzed.(2)The changes of morphology and optical properties were analyzed by regulating the TMIn flow rate and time during growth MQWs of InGaN/GaN platelet micro-arrays structures.When the TMIn flow rate increases,the SEM and AFM characterization results show that the density of the V pit formed by dislocation outcrop and roughness increase,and the results of micro-area Raman spectroscopy show that the crystal quality of the InGaN/GaN micro-arrays structure becomes worse.PL test results show that the peak position of InGaN/GaN platelet micro-arrays structure changes obviously and the correlated color temperature increases obviously.The SEM characterization results show that the morphology of the c facet in the InGaN/GaN platelet micro-arrays structure is very obvious,and the AFM analysis results show that the roughness decreases first and then increases.The results of Raman spectroscopy show that the internal stress in the InGaN/GaN platelet micro-arrays structure decreases first and then increases.The PL results show that the emission peak position of InGaN/GaN platelet micro-arrays structure is consistent blue shift with the increase of excitation power.Finally,the blue shift mechanism is studied by calculating the FWHM of the strongest peak at different excitation power and the PL intensity per unit excitation power.With the increase of MQWs growth time,local state filling effect of In components is becoming increasingly obvious.