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30 January 2001 Two-beam laser heating and melting of GaAs crystal layers
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Proceedings Volume 4157, Laser-Assisted Microtechnology 2000; (2001)
Event: Laser-Assisted Microtechnology 2000, 2000, St. Petersburg-Pushkin, Russian Federation
Liquid-solid phase transitions induced in monocrystalline GaAs by two laser beam irradiation have been studied by a numerical modeling. The modeling was carried out on the basis of solving the Stefan problem in 1D approximation by a finite difference method. Two variants of combined irradiation by Q-switched ruby and CW Nd:YAG lasers were considered. In the first variant nanosecond radiation from a ruby laser induced the surface melting of a GaAs wafer and 'switches on' the absorption of additional CW intensive radiation directed from the back side of the wafer through its volume. Two laser beams are directed from one side in the second variant of combined irradiation. As it follows from the data obtained, the motion of the liquid-solid interface can be controlled by changing the intensity of CW radiation. Because of strong temperature dependence of optical absorption in solid GaAs at (lambda) equals 1064 nm, a heat wave moving toward Nd:YAG laser radiation can arise near the liquid-solid interface in opposite geometry and screen the melt from the CW laser beam. In the case of one- sided geometry the time dependence of melting depth has a nonmonotone character; the crystallization process can be terminated and the melting develops again.
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Sergei P. Zhvavyi, Gennadii D. Ivlev, Elena I. Gatskevich, and Olga L. Sadovskaya "Two-beam laser heating and melting of GaAs crystal layers", Proc. SPIE 4157, Laser-Assisted Microtechnology 2000, (30 January 2001);

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