We have systematically studied the characteristics of Si doping in GaAs grown on (311)A GaAs substrates by molecular beam epitaxy. The growth temperature dependence of Si doping has been investigated. It is found that the conduction-type sharply changes from p-type to n-type with decreasing growth temperature at a critical temperature of 430-480. The highest hole density obtained for uniformly doped layers was 1.51020 cm-3, while for δ-doped layers the sheet hole density as high as 2.61013 cm-2 was achieved. This is the highest hole density ever reported for δ-doped GaAs.

This paper describes a realtime 3D sound localization algorithm to be implemented with the use of a low power embedded DSP. A distinctive feature of this implementation approach is that the audible frequency band is divided into three, in accordance with the analysis of the sound reflection and diffraction effects through different media from a certain sound source to human ears. In the low, intermediate, and high frequency subbands, different schemes of the 3D sound localization are devised by means of an IIR filter, parametric equalizers, and a comb filter, respectively, so as to be run realtime on a low power embedded DSP. This algorithm aims at providing a listener with the 3D sound effects through headphones at low cost and low power consumption.