*Corresponding author, E-mail : naka@ynu.ac.jp TEL : +81-45-339-3854 Electric current dependence on self-cooling device consists of silicon wafers connected to power MOSFET H.Nakatsugawa1,*, Y.Okamoto2, T.Kawahara3 , and S.Yamaguchi 3 1Yokohama National University, 2National Defense Academy, 3Chubu University *Corresponding author, E-mail : naka@ynu.ac.jp TEL : +81-45-339-3854 INTRODUCTION EXPERIMENTAL 　In recent studies, the self-cooling device has been proposed and investigated for the new cooling schemes to remove the heat from the power devices. This device consists of the n-type or p-type thermoelectric material connected to the power devices. Since the electric current flows from the bottom (or the upper) to the upper (or the bottom) direction, the Peltier heat flux and the thermal conduction are transferred from a hot side to a cold side, where a cooling part is made of the p-type (or n-type) thermoelectric material . In this scheme, it is required that thermoelectric materials for the self-cooling device have a high Seebeck coefficient, a high electrical conductivity , and a high thermal conductivity. The single-crystalline Si must be one of the candidate materials for use in the self-cooling device. In fact, we have investigated the self-cooling device using the Sb doped n-type Si wafer and shows the heat removal on the power MOSFET qualitatively. Fukuda et al. suggest that a self-cooling device based on the B doped p-type Si wafer with a high carrier density can show a good heat removal performance. However, it has yet to be shown that a quantitative understanding of single-crystalline n-type or p-type silicon for the self-cooling device is still lacking. The aim of this study is to develop the self-cooling device using the n-type or p-type silicon wafer to estimate the heat removal quantitatively in order to improve the cooling for the power MOSFET. 　The electric current of 40A or 50A flows along the direction of the white arrow by the DC power supply (EX-1500L2, TAKASAGO), where the voltage of 10V is applied between the gate and the source of the power MOSFET. To determine whether the self-cooling device remove the Joule heat from the power MOSFET, we have measured the time dependence of the temperature distribution of the self-cooling device by the infrared thermography (TVS-200EX, NEC Avio). Fig1. Schematic structure of the self-cooling device Fig2. Self cooling-device consisting of the power MOSFET and the n-type Si wafer Fig4. (a) Experimental setup used to estimate the self-cooling device and schematic illustrations , i.e., (b) MOSFET only, (c) MOSFET with n-type Si wafer, and (d) MOSFET with p-type Si wafer, where white arrows show the direction of the electric current (I = 40A or 50A). Fig3. Temperature dependence of (a) the electrical resistivity and (b) the Seebeck coefficient RESULTS AND DISCUSSION 120 minutes 120 minutes 　When electric current of 40A flows, the Joule heat is measured 2.40W from the voltage between the drain and the source. The average temperatures of the upper side of the power MOSFET, that on the power MOSFET, and that of the lower side of the power MOSFET are 23.3℃, 12.6℃, and 7.4℃, respectively,. 　The Joule heat and the Peltier heat are measured 2.50W and 2.66W, respectively. The average temperatures of the upper side of the MOSFET+n-type Si, that on the MOSFET+n-type Si, and that of the lower side of the MOSFET+n-type Si are 24.3℃, 12.1℃, and 7.3℃, respectively,. 　The Joule heat and the Peltier heat are measured 2.43W and 2.85W, respectively. The average temperatures of the upper side of the MOSFET+p-type Si, that on the MOSFET+p-type Si, and that of the lower side of the MOSFET+p-type Si are 24.9℃, 12.1℃, and 7.3℃, respectively,. 120 minutes 120 minutes 　When electric current of 50A flows, the Joule heat is measured 3.85W from the voltage between the drain and the source. The average temperatures of the upper side of the power MOSFET, that on the power MOSFET, and that of the lower side of the power MOSFET are 24.4℃, 15.9℃, and 7.9℃, respectively,. 　The Joule heat and the Peltier heat are measured 4.00W and 3.95W, respectively. The average temperatures of the upper side of the MOSFET+n-type Si, that on the MOSFET+n-type Si, and that of the lower side of the MOSFET+n-type Si are 26.1℃, 13.2℃, and 7.5℃, respectively,. 　The Joule heat and the Peltier heat are measured 3.89W and 4.51W, respectively. The average temperatures of the upper side of the MOSFET+p-type Si, that on the MOSFET+p-type Si, and that of the lower side of the MOSFET+p-type Si are 26.4℃, 12.4℃, and 7.5℃, respectively,. Table I. Average temperatures, VDS, Joule heat, and Peltier heat (I = 40A) Table II. Average temperatures, VDS, Joule heat, and Peltier heat (I = 50A) SUMMARY 　We indicate for the first time the electric current dependence on the self-cooling device and that the average temperature on the power MOSFET is cooled down when the electric current of 50A flows. In particular, the average temperature on the power MOSFET decreases 2.7℃ by the n-type Si wafer and 3.5℃ by the p-type Si wafer. This fact indicates that the n-type or p-type silicon wafers are one of the candidate materials for the self-cooling device. 結論 ACKNOWLEDGMENTS : This study has been partly supported by the Grants-in-Aid for Scientific Research #22560691.