The Site Selectivity of the E-beam Excitation of Eu ion in GaN

GaN is a very promising semiconductor host for rare-earth (RE) based electrically-pumped light emitters. Recently, simulated emission in Eu-doped GaN has been reported under optical excitation, rekindling the hope that an electrically-pumped rare-earth-doped semiconductor laser can be realized. In these laser experiments performed under pulsed UV excitation, it was noted that by changing the resonator length the emission wavelength is shifting suggesting that different types of Eu ions are contributing emphasizing the importance to understand the excitation mechanism for different incorporation sites of the ion. This is the purpose of this work.