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This document is a summary of a special issue in the Journal of Applied Physics on semiconductor physics. The special issue focuses on the research of new semiconductor materials, structures, and devices, as well as the development of characterization methods based on plasma, thermal, elastic, acoustic, and related effects. The articles cover various topics such as photothermal methods, theoretical and experimental models, modern materials like thin films and heterostructures, and imaging techniques. The research presented in this special issue has applications in microelectronics, optoelectronics, solar cells, medical instrumentation, and quantum computing. [Extracted from the article]

We investigate surface phonon propagation in a triangular-lattice phononic crystal of microscopic holes in a gold-coated polymer by time-resolved two-dimensional imaging and by finite-element simulations at sub-gigahertz frequencies. The simulations allow the effects of exciting different points in the crystal lattice to be studied in real space, and also in k-space by spatiotemporal Fourier analysis. The acoustic field in a sub-surface plane below the reach of the holes is also revealed in real-and k-spaces. In addition, we demonstrate pitfalls in the analysis of k-space data when searching for the presence of band gaps. Applications include surface-acoustic wave filter quality control. [ABSTRACT FROM AUTHOR]

We use an ultrafast optical pump and probe technique to investigate the propagation of subgigahertz surface acoustic waves on a 1 mm diameter glass sphere with an aluminum coating. A fiber-based pump setup generates the surface waves and a common-path interferometer images them in the time domain over the sphere surface as they pass through the pole opposite the source of excitation. Fourier analysis allows the acoustic spectrum of the acoustic source to be extracted and waves traveling in opposite directions to be isolated. [ABSTRACT FROM AUTHOR]

We use ultrashort optical pulses to microscopically image carrier and thermal diffusion in two spatial dimensions in pristine and mechanically polished surfaces of crystalline silicon. By decomposing changes in reflectivity in the latter sample into a transient component that varies with delay time and a steady-state component that varies with pump chopping frequency, the influence of thermal diffusion is isolated from that of carrier diffusion and recombination. Additionally, studies using carrier injection density as a parameter are used to clearly identify the carrier recombination pathway. [ABSTRACT FROM AUTHOR]

The problem of the photothermal modulation of optical beams passing through multilayer films is an extremely complex one owing to the inhomogeneously modulated refractive index combined with multiple optical reflections inside the sample. This problem has so far not been given an exact analytical treatment in the field of photothermal probing. We consider here such a treatment for normal-incidence optical probing in reflectance of photothermally modulated single-layer thin-film samples with arbitrary optical constants. The validity of the method is demonstrated by application to a thin transparent film of silica on a silicon substrate. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Required basic features as to 30 Gbpsi recording density for write head are good overwrite O/W, good nonlinear transition shift NLTS, and high frequency performance in half-micron track width. To achieve these, we have developed a new structure, planar yoke write head, combined with SV read head, which is featuring narrow track (physical write track width = 0.35 [micro]m), narrow coil pitch (1.3 [micro]m coil pitch) for short yoke length (16 [micro]m yoke length), 1 layer coil design, and used flat yoke pole while we have been succeeding the advantages of our current stitched pole write head. Regarding the write performance, we compared planar yoke head with current stitched pole head by simulation and actual measurement. Index Terms--Magnetic recording heads, narrow coil pitch, narrow track width, planar yoke head.