Heat transfer efficiency enhanced by annealing treatment in Graphene-LED Structure

Abstract

As semiconductor devices are miniaturized & integrated, the heat generation rate per unit volume when the device is operated has continued to increase. However, the technology of removing heat from devices quickly was still stagnant. So, removing heat from devices is one of the major issue in semiconductor field. But recently, cooling devices using graphene was reported and research has been active to lower the operating temperature of the device by utilizing graphene’s high thermal conductivity. In this paper, the coupling bonding force of each sample (Graphene & LED) was changed through thermal annealing to determine the best transfer of heat(acoustic phonon) when the bonding strength between the two substances are different. Typically, the heat energy in a solid called acoustic phonon causes a reduction in efficiency in photovoltaic devices and electronic speed saturation in electrical devices. For this reason, in terms of efficiency improvement and energy saving, understanding of phononics is a big issue. The bonding strength between the graphene and the sample was determined by means of Raman spectroscopy and the acoustic phonon produced to view the heat transfer rate from each sample (samples without graphene, samples without annealing, 200°C annealing, and samples with 400°C annealing) was measured using ultra-fast pulse laser. The acoustic phonon generated through the pump beam when the internal electric field is momentarily screening by photo carrier, and the analysis of the generated acoustic phonon is measured as a change in the reflectance due to the interaction of the probe beam with the acoustic phonon. The results of the measurements showed that the degree of variation in phase after reflection at the surface was different for each sample, with the largest phase change for samples treated with 200°C annealing. In an additional experiment to see if the results of the above-detection spectroscopy are actually valid, the cooling time measurement, which measures the temperature of the sample using temperature sensor after heating the sample, and the infrared camera, which checks the temperature of the entire area of the actual sample in real time, was taken. As a result, all results of the experiment showed the same tendency and the validity of the experiment was verified. Further work to be done is expected to make considerable progress in removing heat from the device using graphene if the most transferable conditions of the acoustic phonemes are identified and the optimal thermal annealing processing conditions are found at 200°C.