Thermoelectric properties and crystal structures of Au doped SiC/Si composites
Hiroshi Nakatsugawa1), Kensaku Nagasawa1) and Yoichi Okamoto2)
1) Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama
240-8501, Japan E-mail: naka@ynu.ac.jp
2) Department of Material Science and Engineering, National Defense Academy, 1-10-20 Hashirimizu,
Yokosuka 239-8686, Japan E-mail: rshow@nda.ac.jp

Abstract: Silicon semiconductor devices such as Power Metal oxide semiconductor field effecttransistor (Power MOSFET), Insulated gate bipolar transistor (IGBT) and CPU are the mostimportant devices to give us modern life in the present time. When we use these devices in theelectric circuit, the heat removal or the cooling down is one of the most important issues because
the silicon device must be the temperature of 423K or lower to keep its function. The heatgeneration per unit area is the same order of the electric heater in the present devices. There arethree different ways to remove the heat from the silicon devices. One is to use the fin connectedwith the devices, and the second way is to use the fin and fan. The power supply of the fan isnecessary. Usually the size of the fin and fan are larger than the size of the device itself, and thecosts of the fin and fan are sometimes higher than the cost of the device. The third way is to use thePletier element, and this is connected with the large fin and fan usually. The Peltier element and thefan need the different dc power supplies for its cooling, individually. Therefore, if we use the Peltierelement to cool down the silicon devices, the electric power consumption of the system is increased.
This is the one of the reason why the Peltier cooler is not applied for the handy type personal
computers. Recently Yamagushi et al. propose the self-cooling device, which does not need to use
the additional power circuits because the Peltier cooling is done by its selfcurrent. In this system,
the heat flux flow directions of the thermal conduction and the Joule heating are the same for theusual Peltier elements. On the contrary, the direction of the Peltier heat flow is the opposite for theusual Peltier element because of the cooling the high temperature objects. As tabulated in Table 1, it
is clear that high Seebeck coefficient, high electrical conductivity and high thermal conductivity aredesired in the proposed scheme. In this study, we synthesized SiC/Si and Au doped SiC/Si
composites by a conventional solid-state reaction method and studied thermoelectric properties andcrystal structures as a function of temperature.
Table 1. The results of electrical resistivity and conductivity, Hall coefficient, carrier concentration,
Hall mobility, Seebeck coefficient, power factor, thermal diffusivity, sample density, specific heatand thermal conductivity at room temperature, where PSS is a polysilastyrene.
[SiC]0.9 [Si]0.1[SiC]0.8[Si]0.2 + PSS 10%[SiC]0.8 [Si]0.175[Au]0.025 + PSS 10%-3

ρ (10 Ωcm)

9.97

3.82

3.36

σ (1/Ωcm)

100

262

298

109

88.0

92.4

1.19

2.03

2.54

3.09

1.99

1.93

2.02

3.13

3.23
5.74

-6

S (10 V/K)
2-12W/cmK )-2

3S /ρ (102R H (10 cm /C)n (10203/cm )2µ (cm /Vs)

3.10

5.21

3

1.69

2.10

2.17

B (cm /s)

0.32

0.38

0.37C (J/gK)

0.68

0.68

0.66

366

537

524

A (g/cm )2-3

κ (10 W/cmK)