Formation and annealing of dislocation loops induced by nitrogen implantation of ZnO

Guillaume Perillat-Merceroz (1, 2) , Patrice Gergaud (1) , Pascal Marotel (1) , Stéphane Brochen (1) , Pierre-Henri Jouneau (2) , Guy Feuillet (1)

1 CEA-LETI - Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information
2 LEMMA - Laboratoire d'Etude des Matériaux par Microscopie Avancée

Although zinc oxide is a promising material for the fabrication of short wavelength optoelectronic devices, p-type doping is a step that remains challenging for the realization of diodes. Out of equilibrium methods such as ion implantation are expected to dope ZnO successfully provided that the non-radiative defects introduced by implantation can be annealed out. In this study, ZnO substrates are implanted with nitrogen ions, and the extended defects induced by implantation are studied by transmission electron microscopy and X-ray diffraction (XRD), before and after annealing at 900°C. Before annealing, these defects are identified to be dislocation loops lying either in basal planes in high N concentration regions, or in prismatic planes in low N concentration regions, together with linear dislocations. An uniaxial deformation of 0.4% along the c axis, caused by the predominant basal loops, is measured by XRD in the implanted layer. After annealing, prismatic loops disappear while the density of basal loops decreases and their diameter increases. Moreover, dislocation loops disappear completely from the sub-surface region. XRD measurements show a residual deformation of only 0.05% in the implanted and annealed layer. The fact that basal loops are favoured against prismatic ones at high N concentration or high temperature is attributed to a lower stacking fault energy in these conditions. The coalescence of loops and their disappearance in the sub-surface region are ascribed to point defect diffusion. Finally, the electrical and optical properties of nitrogen-implanted ZnO are correlated with the observed structural features.

Mots clés: zinc compounds; annealing; dislocation loops; II-VI semiconductors; ion implantation; semiconductor doping; stacking faults; transmission electron microscopy; X-ray diffraction

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Guillaume Perillat-Merceroz, Patrice Gergaud, Pascal Marotel, Stéphane Brochen, Pierre-Henri Jouneau, et al.. Formation and annealing of dislocation loops induced by nitrogen implantation of ZnO. Journal of Applied Physics, 2011, 109 (2), pp.023513. ⟨10.1063/1.3537917⟩. ⟨hal-00601862⟩