Masayoshi Yamada

Quantitative photoelastic measurement of residual strains in undoped semi‐insulating gallium arsenide

A new quantitative photoelastic method has been developed to measure residual strains in undoped semi‐insulating (001) GaAs substrates for integrated circuits. The absolute values of the shear strain ‖exy‖ and the difference of the expansion and contraction strains ‖eyy−exx‖ existing in the (001) substrate plane are quantitatively determined by using the present method. Their two‐dimensional distribution maps are demonstrated to exhibit fourfold symmetries rotating 45° to each other. The absolute values are found to be of the order of 10−5 at the substrate edges.

Raman Scattering Characterization of Residual Stresses in Silicon-on-Sapphire

In order to characterize the residual stresses in silicon-on-sapphire wafers, polarized Raman scattering measurements were made by probing both from the silicon-free surface side and from the silicon/sapphire interface (sapphire substrate) side at three different wavelengths. These measurements are described here. A theoretical consideration of the Raman tensors and frequency shifts in silicon crystals stressed by unknown forces is also given in this paper. It is found that the residual stresses are not uniform, but are distributed in the direction normal to the silicon film plane. The residual compressive stress is relaxed from the interface toward the silicon-free surface with an accompanying shear stress. The residual compressive stress is estimated to be 6.0×108~13.0×108 N/m2 at the silicon/sapphire interface and 5.5×108~7.5×108 N/m2 at the silicon-free surface.

Raman microprobe study on temperature distribution during cw laser heating of silicon on sapphire

For the first time Raman microprobe experiments have been made to measure the space‐resolved temperature distribution induced in silicon‐on‐sapphire by a stationary elliptical Gaussian laser beam. The algorithm [J. Appl. Phys. 57, 965 (1985)] for solving the nonlinear heat equation in a two‐layer structure has been also extended to include the temperature dependence of laser power absorbed besides the temperature dependencies of thermal conductivity and diffusivity. The problems involved in applying the numerical calculations to the experimental situation are discussed. The numerical calculations of temperature distributions based on the present algorithm are found to give a good agreement with the present Raman microprobe results.

Nonlinear calculation of a temperature profile produced in a two‐layer structure by a scanning cw elliptical laser or electron beam

We present the algorithm to relate the nonlinear heat equation including temperature‐dependent parameters to the Green’s function solution of the linear heat equation for a two‐layer structure. Also derived is the linear solution for an elliptical beam. For silicon‐on‐silicon dioxide, the actual temperature profile based on the present algorithm is numerically calculated and compared with the linear calculation.

Elastic and photoelastic constants of ZnTe measured by Brillouin scattering

The elastic and photoelastic constants of ZnTe crystals have been determined from Brillouin scattering spectra with 90 degrees -scattering geometry at room temperature. From the measured frequency shifts of the Brillouin doublets, the following values are obtained for the elastic constants: C11=7.22+or-0.02, C12=4.09+or-0.06 and C44=3.080.03 in units of 1010 N m-2. From the comparison of the absolute intensities of the Brillouin doublets measured in ZnTe with that in fused quartz whose photoelastic constants are well-known, the following values are determined for the photoelastic constants: P11=0.144+or-0.007, P12=0.094+or-0.005 and P44=0.046+or-0.003.

Microcomputer-based data acquisition and stabilization system for piezoelectrically scanned Fabry-Perot interferomter

A microcomputer-based data acquisition and stabilization system is presented for piezoelectrically scanned plane-parallel Fabry-Perot interferometers which typically required some form of active stabilization system for long-term operation. The microcomputer takes the place of the programable ramp generator, multichannel analyzer, and stabilizer. The control algorithm developed here is workable against strong fluctuations of reference peak. Brillouin scattering spectrum from fused quartz is included to demonstrate the operation of the system.

Optical Absorption for Acoustic Flux in Semiconductive CdS Single Crystal

The optical modulation by acoustoelectric domain has been observed in semiconductive CdS single crystal at room temperature. The nature and mechanism for this optical modulation are discussed, as compared with the Franz-Keldysh effect by the high electric field. The electric field in the domain observed here is saturated by 5 kV/cm, while the optical modulation signals rise linearly. There is little shift of the edge, calculated from the experimental and theoretical results of the Franz-Keldysh effect at the saturation field. Furthermore, the optical modulation signals are clearly visible for several nanoseconds after the applied voltage is removed. Therefore, the optical modulation is not caused by the high electric field but is associated with the intense acoustic flux in the domain. Using the optical modulation technique, the acoustic flux reflected at the anode end is observed even for the application of the voltage. The propagation velocity of acoustic domain, where the voltage is applied perpendicul...

Raman Microprobe Study on Relaxation of Residual Stresses in Patterned Silicon-on-Sapphire

Residual stresses in crystalline silicon islands with concave and convex corners patterned on sapphire substrate are examined by Raman microprobe technique with a spatial resolution of ~1 µm. It is found that the compressive stresses inherently remaining in SOS as-grown by conventional vapor phase epitaxy are relaxed at the edge and corners, depending on the degree of freedom in the relaxing directions.

Observation of Propagating Domain in Semiconductive CdS Using the Optical Probe Method

The optical modulation has been observed in semiconductive CdS single crystals at room temperature by means of the optical probe method using a monochromatic light. The light transmitted through materials with a wavelength corresponding to the intrinsic absorption edge was strongly modulated. The optical modulation observed here is caused primarily by the acoustic flux rather than by the high electric field in the domain. The acoustic domain arrives at its full growth near the point 2 mm from the cathode and travels towards the anode. The aspect of the acoustic domain is subjected to the variation by the strength of the applied electric field, and the domain velocity varies from 2.2×105 cm/sec to 3.0×105 cm/sec according to the increasing applied electric field up to 3040 V/cm.

Nonlinear transmission of intense laser pulse in silicon-on-sapphire

Abstract The time-resolved transmission of a 250 ns excitation pulse itself at 590 nm has been studied during pulsed laser annealing of thin layers of silicon-on-sapphire. The transmission showed a sudden drop arising from the free-carrier absorption and a subsequent saturation not exhibiting the strong absorption expected of ordinary molten silicon.