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Mn as Surfactant for the Self-Assembling of Al x Ga1-x N/GaN Layered Heterostructures.

Devillers T, Tian L, Adhikari R, Capuzzo G, Bonanni A - Cryst Growth Des (2015)

Bottom Line: The structural analysis of GaN and Al x Ga1-x N/GaN heterostructures grown by metalorganic vapor phase epitaxy in the presence of Mn reveals how Mn affects the growth process and in particular, the incorporation of Al, the morphology of the surface, and the plastic relaxation of Al x Ga1-x N on GaN.Moreover, the doping with Mn promotes the formation of layered Al x Ga1-x N/GaN superlattice-like heterostructures, which opens wide perspectives for controlling the segregation of ternary alloys during the crystal growth and for fostering the self-assembling of functional layered structures.

View Article: PubMed Central - PubMed

Affiliation: Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University , Altenbergerstr. 69, A-4040 Linz, Austria.

ABSTRACT

The structural analysis of GaN and Al x Ga1-x N/GaN heterostructures grown by metalorganic vapor phase epitaxy in the presence of Mn reveals how Mn affects the growth process and in particular, the incorporation of Al, the morphology of the surface, and the plastic relaxation of Al x Ga1-x N on GaN. Moreover, the doping with Mn promotes the formation of layered Al x Ga1-x N/GaN superlattice-like heterostructures, which opens wide perspectives for controlling the segregation of ternary alloys during the crystal growth and for fostering the self-assembling of functional layered structures.

No MeSH data available.


Reciprocalspace maps around GaN and AlxGa1–xN(1̅015) for: (a) sample#E and (b) sample #F. The intensity is reported in logarithmic scale.A vertical dashed line along the GaN (1̅01l) and an oblique dashed line joining experimental GaN and AlN (1̅015)are drawn as guides to the eye. The isoconcentration lines are indicatedas continuous lines between the strained and relaxed states.
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fig2: Reciprocalspace maps around GaN and AlxGa1–xN(1̅015) for: (a) sample#E and (b) sample #F. The intensity is reported in logarithmic scale.A vertical dashed line along the GaN (1̅01l) and an oblique dashed line joining experimental GaN and AlN (1̅015)are drawn as guides to the eye. The isoconcentration lines are indicatedas continuous lines between the strained and relaxed states.

Mentions: This result is confirmed by XRD experiments.Reciprocal space mapshave been measured around the (1̅015) reflection of GaN andAlxGa1–xN and are reported in Figure 2 for samples#E and #F. The shape and position of this peak appear to be differentfor the two samples: the center of the peak is shifted toward lowerin-plane lattice parameters in the case of the Mn-free sample. Here,the average lattice parameter of the layer does not fit the one ofGaN, which indicates a plastic relaxation of the crystal lattice.In fact, the peak is neither aligned with the dashed line, which correspondsto a fully relaxed layer, nor with the one corresponding to a fullystrained state, which points to an intermediate strain state. Furthermore,the peak is particularly broad and actually spreads over the wholerange between strained and relaxed state. In comparison, in the presenceof Mn, the (1̅015) reflection of AlGaN is very narrow in Qx and vertically aligned withthe (1̅015) of GaN, which confirms the strained state of thelayer already evidenced by surface microscopy. The Al concentrationis comparable in the two samples; the peak of the layer containingMn and not relaxed is shifted toward higher values of Qz due to the limited compressibilityof the material. In addition, this peak exhibits an unexpected broadeningalong the Qz direction,which suggests the presence of AlxGa1–xN with different Al concentrations.To quantify the Al content in the films from the position of the (1̅015)peak, we assume a linear variation of the out-of-plane lattice parameterwith the Al content in the whole range of concentrations from GaNto AlN (Vegard’s law). In the completely relaxed case, theAl concentration is given by xAl = ((cAlGaN – cGaN)/(cAlN – cGaN)). In the perfectly strained case, it is necessary to adda prefactor to take into account the elongation of the lattice alongthe c direction when the crystal is elongated alongthe a-axis. The Al concentration is then obtainedthrough xAl = ((1 – ν)/(1+ ν)(cAlGaN – cGaN)/(cAlN – cGaN)), where ν is the Poisson coefficient(0.19 and 0.21 for GaN and AlN respectively1). The calculated Al concentration is thus in the considered sample(12 ± 1)% for the partially relaxed Mn-free layer (sample #E).For the Mn-containing layer (sample #F), the two main peaks relatedto AlxGa1–xN correspond to Al contents of 12.8% and 14.3%, respectively.


Mn as Surfactant for the Self-Assembling of Al x Ga1-x N/GaN Layered Heterostructures.

Devillers T, Tian L, Adhikari R, Capuzzo G, Bonanni A - Cryst Growth Des (2015)

Reciprocalspace maps around GaN and AlxGa1–xN(1̅015) for: (a) sample#E and (b) sample #F. The intensity is reported in logarithmic scale.A vertical dashed line along the GaN (1̅01l) and an oblique dashed line joining experimental GaN and AlN (1̅015)are drawn as guides to the eye. The isoconcentration lines are indicatedas continuous lines between the strained and relaxed states.
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fig2: Reciprocalspace maps around GaN and AlxGa1–xN(1̅015) for: (a) sample#E and (b) sample #F. The intensity is reported in logarithmic scale.A vertical dashed line along the GaN (1̅01l) and an oblique dashed line joining experimental GaN and AlN (1̅015)are drawn as guides to the eye. The isoconcentration lines are indicatedas continuous lines between the strained and relaxed states.
Mentions: This result is confirmed by XRD experiments.Reciprocal space mapshave been measured around the (1̅015) reflection of GaN andAlxGa1–xN and are reported in Figure 2 for samples#E and #F. The shape and position of this peak appear to be differentfor the two samples: the center of the peak is shifted toward lowerin-plane lattice parameters in the case of the Mn-free sample. Here,the average lattice parameter of the layer does not fit the one ofGaN, which indicates a plastic relaxation of the crystal lattice.In fact, the peak is neither aligned with the dashed line, which correspondsto a fully relaxed layer, nor with the one corresponding to a fullystrained state, which points to an intermediate strain state. Furthermore,the peak is particularly broad and actually spreads over the wholerange between strained and relaxed state. In comparison, in the presenceof Mn, the (1̅015) reflection of AlGaN is very narrow in Qx and vertically aligned withthe (1̅015) of GaN, which confirms the strained state of thelayer already evidenced by surface microscopy. The Al concentrationis comparable in the two samples; the peak of the layer containingMn and not relaxed is shifted toward higher values of Qz due to the limited compressibilityof the material. In addition, this peak exhibits an unexpected broadeningalong the Qz direction,which suggests the presence of AlxGa1–xN with different Al concentrations.To quantify the Al content in the films from the position of the (1̅015)peak, we assume a linear variation of the out-of-plane lattice parameterwith the Al content in the whole range of concentrations from GaNto AlN (Vegard’s law). In the completely relaxed case, theAl concentration is given by xAl = ((cAlGaN – cGaN)/(cAlN – cGaN)). In the perfectly strained case, it is necessary to adda prefactor to take into account the elongation of the lattice alongthe c direction when the crystal is elongated alongthe a-axis. The Al concentration is then obtainedthrough xAl = ((1 – ν)/(1+ ν)(cAlGaN – cGaN)/(cAlN – cGaN)), where ν is the Poisson coefficient(0.19 and 0.21 for GaN and AlN respectively1). The calculated Al concentration is thus in the considered sample(12 ± 1)% for the partially relaxed Mn-free layer (sample #E).For the Mn-containing layer (sample #F), the two main peaks relatedto AlxGa1–xN correspond to Al contents of 12.8% and 14.3%, respectively.

Bottom Line: The structural analysis of GaN and Al x Ga1-x N/GaN heterostructures grown by metalorganic vapor phase epitaxy in the presence of Mn reveals how Mn affects the growth process and in particular, the incorporation of Al, the morphology of the surface, and the plastic relaxation of Al x Ga1-x N on GaN.Moreover, the doping with Mn promotes the formation of layered Al x Ga1-x N/GaN superlattice-like heterostructures, which opens wide perspectives for controlling the segregation of ternary alloys during the crystal growth and for fostering the self-assembling of functional layered structures.

View Article: PubMed Central - PubMed

Affiliation: Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University , Altenbergerstr. 69, A-4040 Linz, Austria.

ABSTRACT

The structural analysis of GaN and Al x Ga1-x N/GaN heterostructures grown by metalorganic vapor phase epitaxy in the presence of Mn reveals how Mn affects the growth process and in particular, the incorporation of Al, the morphology of the surface, and the plastic relaxation of Al x Ga1-x N on GaN. Moreover, the doping with Mn promotes the formation of layered Al x Ga1-x N/GaN superlattice-like heterostructures, which opens wide perspectives for controlling the segregation of ternary alloys during the crystal growth and for fostering the self-assembling of functional layered structures.

No MeSH data available.