Vibrational spectroscopy of OH-shallow-donor complexes in Ga₂O₃

Si and Ge on a Ga(1) site are n-type dopants in Ga₂O₃ [1,2].  Si impurities are also responsible for the unintentional n-type doping of Ga₂O₃.  Recent experiments show that the Si donor can be passivated by H [3].  A Si-doped epitaxial layer grown by MBE and a Ge-doped layer fabricated by ion implantation were obtained for our studies.  The introduction of H and D by plasma treatment into these Ga₂O₃ samples gave rise to OH-Si and OH-Ge complexes and the corresponding OD complexes.  The vibrational frequencies of the OH-Si and OH-Ge complexes are 3478 and 3425 cm^-1 (77K), respectively, and show a strong dependence on the donor impurity.  The polarization properties, temperature dependences, and annealing stabilities of these OH-donor complexes have also been investigated to obtain clues about the microscopic structures of the defects.