Rare Earth Ion Implantation in GaN: Damage Formation and Recovery
F. Glouxa, P. Ruteranaa, T. Wojtowicza, K. Lorenzb and E. Alvesb
aSIFCOM, UMR 6176, CNRS-ENSICAEN, 14050 Caen, France
bInstituto Tecnológico e Nuclear, EN10, 2686-953 Sacavém, Portugal
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Received: 17 06 2006;
Rare earth ions implanted GaN has been investigated by transmission electron microscopy versus the fluence, using Er, Eu or Tm ions at 150 keV or 300 keV and at room temperature. Point defect clusters and stacking faults are generated from low fluences (7×1013 at/cm2), their density increases with the fluence up to the formation of a highly disordered layer at the surface. This highly disordered layer is observed from a threshold fluence of 3×1014 at/cm2 at 150 keV and 3×1015 at/cm2 at 300 keV, and appears to be composed of voids and misoriented nanocrystallites. Its thickness rapidly increases with the fluence, and then saturates. Both basal and prismatic stacking faults were observed. Basal stacking faults are I1 in majority, but E or I2 have also been identified. I1 basal stacking faults propagate easily through GaN by folding from basal to prismatic planes. Channelling implantation, increasing the implantation temperature from room temperature to 500ºC, or implanting through a 10 nm thick AlN cap reduce the crystallographic damage, particularly by retarding the formation of the highly disordered layer. Implanting through the AlN cap allows the highly disordered layer formation threshold fluence to be increased by one order of magnitude, as well as the annealing at high temperature (1300ºC) which brings about a strong optical activation of the rare earths.
DOI: 10.12693/APhysPolA.110.125
PACS numbers: 61.72.Vv, 61.72.Nn, 68.37.Lp, 81.05.-t