Single-frequency DFB laser diodes at visible wavelengths grown with low temperature remote plasma chemical vapor deposition p-AlGaN

High-efficiency green laser diodes remain a challenge for researchers and manufacturers due to several factors intrinsic to the InAlGaN material system. Notably, the high indium content quantum wells (QW) are sensitive to thermal damage in the form of indium segregation, particularly when the QWs are exposed to the high-temperature growth steps of the ptype AlGaN cladding layers in MOCVD. This paper presents device results from blue distributed feedback (DFB) laser diodes grown entirely by MOCVD compared to material grown by MOCVD through the active region and overgrown with low-temperature p-AlGaN using remote plasma chemical vapor deposition (RPCVD). Preliminary data demonstrate comparable performance from MOCVD-only and MOCVD with RPCVD p-cladding, showing a full-width at half maximum emission of 3 pm and side mode suppression ratio of 19 dB. RPCVD enables the growth of high-quality ptype AlGaN layers at temperatures below the thermal damage threshold of In-rich QWs, leading to longer wavelength devices. The degree of thermal damage to the In-rich green QWs is assessed using fluorescence microscopy to directly compare the RPCVD-enhanced p-AlGaN growths at various growth temperatures over all-MOCVD n-side and green quantum wells.