Spectral Emissivity of Silicon

Abstract

The emissivity of silicon was observed in the spectral region from 0.4 to 15 µ at various temperatures from 340°K to 1070°K by using two n-type specimens with the resistivity of 15 ohm-cm and 7×10-3 ohm-cm at 300°K, respectively. The thermal radiation of silicon consists of three types due to band-to-band transition, free carriers and lattice vibration. It was made clear from the emissivity measurement that, in a pure specimen, the radiation due to lattice vibration is conspicuous at low temperatures, while that due to free carriers is predominant at higher temperatures, and that, in a doped specimen, the radiation due to free carriers is predominant even at low temperatures. The observed emissivity is close to the theoretical formula represented by the refractive index n and the extinction coefficient k. The temperature dependence of n and k is shown and a brief discussion is also added.

Temperature Measurement of Semitransparent Silicon Wafers Based Upon Absorption Edge Wavelength Shift

“…Radiation thermometry is a typical method meeting this requirement [4], but its accuracy is limited by the uncertainty in the emissivity of the silicon wafer and the thin film layers deposited on the wafer, such as oxide films. The radiative properties of silicon wafers are complex, and change during processing [4][5][6][7][8][9]. In order to overcome this problem, we developed a radiation thermometry method that enables the simultaneous measurement of emissivity and temperature of a silicon wafer, based upon a polarization technique [10].…”

“…There are various absorption mechanisms over a wide spectral range [5,7,[11][12][13][14]. As the wavelength increases, the photon energy decreases until it becomes lower than the minimum energy gap in the silicon band structure.…”

Micro/mesoscale combustion based portable power generating system

“…As one of the most prevalent materials for micro electromechanical systems (MEMS), silicon was widely used for manufacturing prototypes of micro-power generating devices and micro-propulsion systems owing to its favourable mechanical and thermal properties [11,13,14]. Moreover, silicon can offer an emissivity of 0.6 -0.7 at elevated temperatures in the convertible band of the PV cells [191], and is therefore considered a reasonable emitter material serving for the purpose of TPV power generation. Table 6.1 has summarised the typical thermal properties of quartz and silicon wafers used in this study.…”

“…Satō et al [191] showed that the emissivity for pure silicon specimen first increased as the temperature increased, and then maintained at a constant value (∼0.7 in their work) across the whole IR camera band (7.5 -13 µm) of interest after the temperature increased beyond 870 K. The emissivity for "heavily" doped silicon (doping concentration of ∼8 × 10 18 cm −3 ), however, was found to be much more invariant to the temperature with a band-averaged value of ∼0.75 [191]. The silicon wafers used in this work were described as "lightly" doped by the manufacturer, but the specific doping level was unknown.…”

“…This is because unlike the highly transmissive quartz wafer (in the PV cell convertible band) which has an extremely low emissivity (emissivity = 1 -transmissivity -reflectivity, according to Kirchhoff's Law), the silicon wafer which is only partially transmissive in this band has a reasonably high emissivity of 0.6 -0.7 at elevated temperatures [191]. Therefore, radiation from the silicon surface becomes a primary mechanism (much more prevalent than the flame luminescence) for the TPV power output.…”