InAlGaN optical emitters - laser diodes with non-epitaxial cladding layers and ultraviolet light-emitting diodes

We describe recent work on InGaN lasers and AlGaN UV LEDs at the Palo Alto Research Center (PARC). The presentation includes results from InGaN laser diodes in which the usual epitaxial upper cladding layer is replaced with an evaporated or sputtered non-epitaxial material, such as indium tin oxide, silver, or a silver-palladium-copper alloy [1, 2]. Non-epitaxial cladding layers offer several advantages to long wavelength InGaN laser diodes, such as eliminating the need to expose vulnerable InGaN active layers to the high temperatures required for growing conventional p-AlGaN cladding layers subsequent to the active layer growth. The presentation also discusses our recent results on AlGaN UV LEDs. UV LEDs with 300 micron square geometries operating at lambda = 325 nm exhibit output powers of 13 mW with differential quantum efficiencies of 0.054 W/A measured under wafer-level, unpackaged condition with no heat sink. LEDs operating at lambda = 290 nm under similar test conditions display output powers of 1.6 mW for large-area 300 mu m X 1 mm devices.