Undoped semi‐insulating GaAs epitaxial layers and their characterization

Wafer annealing was applied to undoped conductive GaAs epitaxial layers grown by the chloride chemical vapor deposition method in order to realize semi‐insulating GaAs epitaxial layers. It was found that, by wafer annealing at temperatures higher than 950 °C, semi‐insulating epitaxial layers with a resistivity higher than 107 Ω cm and a mobility higher than 5000 cm2/V s can be obtained. The material quality has been evaluated by Hall measurement, isothermal capacitance transient spectroscopy, deep level transient spectroscopy, scanning photoluminescence, AB etching, ion implantation, and activation efficiency measurement. It was concluded that the semi‐insulating behavior of undoped GaAs epitaxial layers is due to the increase of the EL2 concentration to the level of 5×1015 cm−3 realized by wafer annealing. The present material does not show any cell structures which are inherent to bulk GaAs materials. It was found to be of the best quality ever reported from the viewpoint of various material characteriz...