Sulfur passivation has been shown to be effective for light intensity enhancement of AlGaInP light-emitting diodes (LEDs). The scribed AlGaInP LED die was dipped in (NH4)2Sx to passivate the LED surface. An effective suppression of surface recombination was observed. The leakage current of AlGaInP LEDs decreased from 1.4 ×10-6 A (untreated samples) to 7×10-7 A ((NH4)2Sx-treated ones) at a reverse bias of 10 V. A 5-fold increase in the light intensity of the (NH4)2Sx-treated AlGaInP LEDs was observed relative to that of the untreated LEDs.

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The light emitting diode (LED) is widely used in modern solid-state lighting applications, and its output efficiency is closely related to the submounts’ material properties. Most submounts used today, such as low-power printed circuit boards (PCBs) or high-power metal core printed circuit boards (MCPCBs), are not transparent and seriously decrease the output light extraction. To meet the requirements of high light output and better color mixing, a three-dimensional (3-D) stacked flip-chip (FC) LED module is proposed and demonstrated. To realize light penetration and mixing, the mentioned 3-D vertically stacking RGB LEDs use transparent glass as FC package submounts called glass circuit boards (GCB). Light emitted from each GCB stacked LEDs passes through each other and thus exhibits good output efficiency and homogeneous light-mixing characteristics. In this work, the parasitic problem of heat accumulation, which caused by the poor thermal conductivity of GCB and leads to a serious decrease in output efficiency, is solved by a proposed transparent cooling oil encapsulation (OCP) method.