¡@¡@A high efficient packaging technique was proposed for power InGaN light emitting diodes( LEDs ).In this approach , sub-mounts based on Si bench technology were used to provide a fact heat conducting channel between the LEDs and the cases.Two different structures of the Si sub-mounts were used, namely, a conventional Si block and a Si block with a copper-filled V-groove. ¡@¡@The thermal resistance of the two different sub-mounts were measured and compared. For a 45mil power LED biased at 1W, thermal resistance of 12.77¢J/W and 18.79¢J/W were measured for the Si sub-mount and the Si sub-mount with copper-filled V-groove. We believe the better thermal resistance of the sub-mount with copper-filled V-groove is due to high thermal conductivity of the copper.

Since the AlGaInN alloy has a continuous direct bandgap from about 0.7 eV (InN) to 6.2 eV (AlN), nitride-based materials can cover most of the electromag netic spectrum from near-infrared to ultraviolet. Based on this feature, nitride based light-emitting diode (LED) devices have been widely used. With the first commercialization of blue LED devices in 1993, the LED industry became more and more important in the field of lighting. As a typical light-emitting material, LED devices are not only determined by their own components, but also their luminous efficiency is one of the focuses of attention. Generally speaking, the standard for measuring the luminous efficiency of LED devices is the ratio of the number of injected carriers to the number of emitted photons, that is, the external quantum efficiency (EQE). In order to obtain a higher EQE, it can be improved from three aspects, namely internal quantum efficiency (IQE), light extraction ef ficiency (LEE) and injection efficiency (IE). However, since LED devices are often grown by vapor phase epitaxy, the epitaxial growth substrate often absorbs the light emitted by the LED device, thereby reducing the EQE of the entire device and affecting the luminous efficiency. Especially as the light-emitting wavelength of LEDs becomes longer and longer, the EQE of LED devices tends to drop from more than 80% to 4% or even lower (the decline of red LEDs will be more signif icant). At the same time, as the size of LED devices decreases, the proportion of damage caused by the mesa etching process and the surface recombination area of devices (such as Micro LED devices) increases accordingly, and EQE will also show a clear downward trend. Therefore, in addition to further improving EQE through internal quantum efficiency, increasing LEE as much as possible through structural changes is also a key point to improve EQE. In our study, based on our group’s own grown red LEDs, we successfully transferred structured vertical InGaN red LEDs from Si(111) substrates to new substrates, achieving further improvements in LEE. At the same time, it also provides options for applying this technology to LED devices and micro-LED devices of various wavelengths in the future. The LED device with the vertical structure has a low turn-on work ing voltage and a small series resistance. The whole process adopts dry etching technology, which makes the process more precise and reliable. Compared to standard LED devices, the operating voltage and series resistance of LEDs are changed from 30Ω to less than 10Ω respectively, and the LEE is improved by 70%, which is mainly attributed to the removal of the light-collecting substrate and the use of metal reflective layers to improve light extraction efficiency. Furthermore, although the process is an improvement over LEE, this structure-based process improvement can be used for LEDs of various wavelengths as well as micro-LEDs in the future. This typical substrate transfer technique can transfer very thin (3 micron) LED structures from one substrate to another without damaging the device itself, thus providing a way to realize flexible substrates in the near future.