Growth and Optical Properties of Quaternary InAlGaN for 300 nm Band UV-Emitting Devices

Abstract

We demonstrated room temperature (RT) intense ultraviolet (UV) emission with wavelength in the range of 300–340 nm from InxAlyGa1—x—yN quaternary alloys grown by metal organic vapor phase epitaxy (MOVPE). We found that the UV emission is considerably enhanced by In segregation upon introducing approximately 5% of In into AlGaN. We fabricated multi-quantum wells (MQWs) consisting of Inx1Aly1Ga1—x1—y1N wells and Inx2Aly2Ga1—x2—y2N barriers. The intensity of the 320 nm band emission from the InAlGaN-based MQWs was as strong as that of the 410 nm band emission from InGaN-based QWs at RT. We also fabricated an InAlGaN/InAlGaN single (S)QW and clearly observed In segregation of submicron size from cathodoluminescence (CL) images. The temperature dependence of photoluminescence (PL) emission for InAlGaN-based QWs was greatly improved in comparison with that of GaN- or AlGaN-based QWs. We also achieved a hole concentration of 3 × 1017 cm—3 for large bandgap (around 4 eV) quaternary InxAlyGa1—x—yN by Hall measurements. Finally, we fabricated UV light-emitting diodes (LEDs) using InAlGaN active region and achieved efficient 345 nm emission.