Hydrogen and interstitial Mn complexes in MnxGa1-xAs dilute magnetic semiconductors

Complexes formed by H and Mn interstitials (Mn-int) in MnxGa1-xAs dilute magnetic semiconductors (DMSs) have been investigated by using first-principles density functional theory (DFT) methods both in gradient corrected spin density and Hubbard U approximations. In agreement with previous results for complexes of H with substitutional Mn (Mn-Ga), present results confirm the importance of electron correlation effects, as the Hubbard U treatment weakens the H-Mn bonds even in the H-Mn-int complexes. They also indicate that H compensates (without passivating) the Mnint by forming Mn-int-H donor-acceptor (D-A) pairs and, then, Mn-int-H complexes. In the H-Mn-int and H-Mn-Ga complexes, the H-Mn D-A interaction is always mediated by a host atom, thus leading to the formation of H-Ga bonds for interstitial Mn and of H-As bonds for substitutional Mn. This implies quite different H vibrational frequencies for the H-Mn-int and H-Mn-Ga complexes, thus suggesting that H can be used as a probe to discriminate between the two Mn forms through vibrational spectroscopy measurements. Finally, a higher stability of the H-Mn-int with respect to the H-Mn-Ga complexes has been found, which suggests the use of hydrogenation procedures to control the effects of Mnint on the MnxGa1-xAs properties.