[OPTICAL REVIEW Vol. 1, No. 2 (1994) 299-303

Effects of Ambient Gas and Temperature on Photo-Acoustic Displacement for Semiconductors

Shingo SUMIE and Hiroyuki TAKAMATSU

Electronics Research Laboratory, Kobe Steel, Ltd., 1-5-5, Takatsukadai, Nishi-ku, Kobe, Hyogo, 651-22 Japan

(Accepted September 6, 1994)

The effects of the pressure of ambient gas and sample temperature on photo-acoustic displacement (PAD) were studied quantitatively using an extremely sensitive laser interferometric probe. For silicon, the PAD signal measured at atmospheric pressure increased by about 18% as compared to that obtained in a vacuum, and varied by less than 0.7% for a change in pressure of 5% around 1 atm. This effect was attributed to the decrease in refractive index of the gas adjacent to the sample. Temperature rise caused PAD to increase proportionally, and for GaAs, PAD varied 0.4% per degree. The variation of PAD with temperature was accurately explained by the temperature dependence of thermal expansion coefficient and thermal conductivity of the sample.

Key words : photo-acoustic displacement, interferometer, thermal expansion, thermal expansion coefficient, thermal conductivity, silicon, gallium-arsenide, ion implantation, gas, temperature