Preparation and Increased Optical Properties of Large-Area AlInGaN LEDs with Mesoporous AlGaN-Distributed Bragg Reflectors

2 in. mesoporous AlGaN (MP-AlGaN)distributed Bragg reflectors(DBRs) were obtained via electrochemical etching in 0.25 M oxalicacid solution and then were used as the substrate for growth of thelarge-area and highly reflective AlInGaN light-emitting diodes (LEDs)via the metal-organic chemical vapor deposition (MOCVD) technology.Compared to reference AlInGaN LEDs without DBRs, the wafer-scale AlInGaNLED structure with MP-AlGaN DBRs exhibit a nearly sevenfold increasedluminescence intensity ascribed to the light reflection effect ofMP-AlGaN DBRs and increased internal quantum efficiency of the multiplequantum wells (MQWs) layer. The blue shift of the PL peak is due tostress relaxation in the AlInGaN MQWs layer. Moreover, AlInGaN LEDswith MP-AlGaN DBRs present an increased luminescence lifetime comparedwith that of reference AlInGaN LEDs, which confirms the improved crystallinequality of the AlInGaN MQWs layer. The2 in. mesoporous AlGaN (MP-AlGaN) distributed Braggreflectors (DBRs) were obtained by electrochemical etching in an oxalicacid solution and then were used as the substrate in the growth ofthe large-area and highly reflective AlInGaN LEDs via the metal-organicchemical vapor deposition (MOCVD) technology. Compared to the samplewithout DBRs, the wafer-scale AlInGaN LED structure with the MP-AlGaNDBRs exhibit a nearly sevenfold increased luminescence intensity,which is attributed to the light reflection effect of the bottom MP-AlGaNDBRs and improved internal quantum efficiency (IQE) of the multiplequantum wells (MQWs) layer. The blue shift of the PL peak is due tothe stress relaxation in the AlInGaN MQWs layer because of the electrochemicaletching and regrowth processes. Additionally, AlInGaN LEDs with theMP-AlGaN DBRs present an increased PL lifetime compared with thatof reference AlInGaN LEDs, which confirms the improved crystallinequality of the AlInGaN MQWs layer.