Abstract

Gallium nitride doped with europium (GaN:Eu), one of the rare-earth elements, has been attracting much attention as the material for red light-emitting devices [1-4]. To improve the device performance, further characterization of the material itself and carrier dynamics is essential. Laser terahertz (THz) emission microscopy (LTEM) is a new method to unveil the photocarrier dynamics, built-in fields, and so on, of the wide bandgap semiconductors. The examples are that one can estimate the local bandgap energies directly [5,6], study the potentials and built-in fields at the surfaces and interfaces [7-9], and visualize the spontaneous polarization domains on the m-plain of GaN [10]. In this work, we study the optical response of the GaN:Eu/unintentionally (UID)-GaN layered structures and discuss the Eu doping effects in GaN by observing THz radiation.

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