Mechanisms of Implantation Damage Formation in Al_xGa_1–xN Compounds

Abstract

Al x Ga 1−x N alloys, covering the entire compositional range (0 ≤ x ≤ 1), were implanted at room temperature with 200 keV argon (Ar) ions to fluences ranging from 1 × 10 13 to 2 × 10 16 Ar/cm 2 . The damage formation mechanisms and radiation resistance of Al x Ga 1−x N alloys were investigated combining in situ Rutherford backscattering spectrometry/channeling (RBS/C) and ex situ X-ray diffraction (XRD) in order to assess the damage profiles and the elastic response of the material to radiation. For all compounds, damage buildup proceeds in four stages revealing a saturation of the defect level for high fluences without any sign of amorphization. Surprisingly, in this high fluence regime, RBS/C reveals higher defect levels in samples with high AlN concentrations in contrast to the common believe that AlN is more radiation resistant than GaN. A model is proposed ascribing this behavior to a lower defect recombination cross section at room temperature combined with the formation of stable extended defects. The processes are probably dependent on the collision cascade density, that is, the mass of the implanted ions. XRD shows that implantation leads to the incorporation of large lattice strain in the implanted layer which increases with increasing fluence. Above a threshold fluence, an abrupt change of the elastic properties of the crystals is observed and strain saturates in the entire implanted region. This threshold fluence is reached earlier for GaN than for Al x Ga 1−x N alloys with x > 0.

The effect of ion implantation on structural damage of сompositionally graded AlGaN layers

“…Similar behavior of the bimodal damage was also demonstrated in Ref. [9] for Al x Ga 1-x N alloys (x = 0, 0.13, 0.47, 0.7, and 1) implanted with Ar + ions. In addition, the X-ray diffraction (XRD) analysis has shown that the implantation with Ar + ions introduces hydrostatic strain resulting from the expansion of the c-lattice parameter.…”

Impact of implantation geometry and fluence on structural properties of AlxGa1-xN implanted with thulium

“…Efficient dynamic annealing leads to low damage accumulation rates for low and medium fluences followed by a strong increase of damage level at higher fluences due to the formation of extended defects. 28,30,45 Lorenz et al 19 studied the relative defect density as a function of the fluence, for random and channeled implantation in AlN implanted with Eu using similar conditions as in the present study. These authors showed that for random implantation the strong increase of defect accumulation rate starts at $1 Â 10 15 Eu cm À2 while for channeled implantation this increase is delayed to fluences of $2 Â 10 15 Eu cm À2 , in agreement with our results (Figure 3).…”

“…28,29 Faye et al studied the AlGaN alloys under Ar implantation and showed a four stage damage build-up process, without reaching amorphisation at saturation damage level and with higher defect levels reached for high AlN content samples. 30 In the present work, we doped Al x Ga 1-x N samples with Tm ions by ion implantation under random and channeled implantation geometries. A detailed study of the structural properties was performed with Rutherford backscattering spectrometry/channeling, transmission electron microscopy, and X-ray diffraction.…”

Ion‐beam induced effects in multi‐layered semiconductor systems

“…Much less work was done on AlN (see e.g., Refs. and references therein). Both materials have in common that the concept of critical temperatures as explained in Section 2.1 does not apply.…”

“…At Ar ion fluences above 1 × 10 15 cm −2 complex tangles of defect clusters and extended defects form which saturate in a second plateau (for more detailed descriptions of the microscopic processes see Ref. and references therein). Similar fluence dependences are also observed for heavier ion species .…”