Improvement Of GaAs Microtips Grown By Selective Liquid-phase Epitaxy

Information storage has been becoming an essential issue in this digital age. The past couple of decades witnessed the explosive increase of the capacity of the information and the remarkable miniaturization of electronic devices. Those trends continue to demand new recording technologies and materials that could combine the virtues of high density, fast response, long retention time, and re-writing capability. As predicted, the current silicon-based computer circuits are reaching their physical limits. Further miniaturization of the electronic components and increase in data storage density are vital for the next generation of IT equipment. Scanning near-field optical microscopy(SNOM) is a novel tool for the research down to nanometer scale. It utilizes the evanescent field confined at the tiny aperture for providing images of object surfaces with a resolution beyond the classical optical diffraction limit. For this reason. SNOM enables the realization of nanometer scale data storage. Generally speaking, SNOM sensor is composed of three main parts:semiconductor laser, photoelectronic detector and the microtip. Since microtip is one essential part of SNOM, the fabrication of high quality microtips has become a key issue.To obtain high-quality microtips, a simple and reproducible technique for fabricating GaAs microtips is presented. In this method, the GaAs microtips are grown by selective liquid-phase epitaxy, including mask preparation, photolithography, wet etching and liquid phase epitaxial growth. However, the residual melt can be seen obviously in one surface of all the pyramidal microtips, which adversely affects the appearance and performance of microtips. To solve this problem, we modify the graphite boat, which is from traditional horizontal sliding graphite boat to rotatable graphite boat. By rotating the rotatable graphite boat by 180°at the end of the growth, the residual growth solution separates from the GaAs substrate due to gravity. Scanning electron microscope is employed to observe the surface morphologies of the GaAs microtips. The results show that by rotating the graphite boat instead of horizontal sliding at the end of the growth, the size of the residual melt is remarkably reduced. The quality of the GaAs microtips is improved, which is of great significance to the application of SNOM sensor.