The fabrication technology for photonic crystals (PhCs) pertaining to the near-infrared region is mature, and the development of highly functional PhCs using low-symmetry nanoholes is rapidly progressing. In the visible region, InGaN/GaN systems that have good luminescent and electrical properties are the most promising candidate materials for such types of highly functional PhCs, but the development is not progressing. In this study, we report on the basic design parameters and a new fabrication method for InGaN/GaN-based PhC membranes by combining hydrogen environment anisotropic thermal etching (HEATE) based on hydrogen-assisted thermal decomposition and nitric acid wet etching of the AlInN sacrificial layer. Using this method, we fabricated high-quality InGaN/GaN multiple-quantum-well PhC membrane structures having six-membered rings of well-formed fine equilateral triangular nanoholes with a side length of 100 nm. Enhanced green room-temperature photoluminescence with an intensity nine times higher than that of as-grown wafers was observed for the PhC membrane.

A fully-automatic torque magnetometer controlled by a minicomputer was developed. The sample rotation mechanism enables to determine the crystallographic orientation of a ferromagnetic single crystal automatically within an accuracy of 1° in a few hours by orientating the crystal so as to make the sin 4θ component of the torque curve maximum. A new type of frictionless bearing was adopted to support the sample holder. The range of the measurable torque was 103 to 105 dyne·cm with an accuracy of 1%.