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The role of dislocation-induced scattering in electronic transport in GaxIn1-xN alloys.

Donmez O, Gunes M, Erol A, Arikan CM, Balkan N, Schaff WJ - Nanoscale Res Lett (2012)

Bottom Line: Hall effect measurements are performed at temperatures between 77 and 300 K.Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent.In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Science Faculty, Department of Physics, Istanbul University, Vezneciler, Istanbul 34134, Turkey. arikan@istanbul.edu.tr.

ABSTRACT
Electronic transport in unintentionally doped GaxIn1-xN alloys with various Ga concentrations (x = 0.06, 0.32 and 0.52) is studied. Hall effect measurements are performed at temperatures between 77 and 300 K. Temperature dependence of carrier mobility is analysed by an analytical formula based on two-dimensional degenerate statistics by taking into account all major scattering mechanisms for a two-dimensional electron gas confined in a triangular quantum well between GaxIn1-xN epilayer and GaN buffer. Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent. Carrier density is almost temperature independent and tends to increase with increasing Ga concentration. The weak temperature dependence of the mobility may be attributed to screening of polar optical phonon scattering at high temperatures by the high free carrier concentration, which is at the order of 1014 cm-2. In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results. Our results reveal that in the samples with lower Ga compositions and carrier concentrations, alloy and interface roughness scattering are the dominant scattering mechanisms at low temperatures, while at high temperatures, optical phonon scattering is the dominant mechanism. In the samples with higher Ga compositions and carrier concentrations, however, dislocation scattering becomes more significant and suppresses the effect of longitudinal optical phonon scattering at high temperatures, leading to an almost temperature-independent behaviour.

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Experimental and calculated temperature dependence of mobility curves for (a) Ga0.06In0.94 N and (b) Ga0.32In0.68 N.
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Figure 2: Experimental and calculated temperature dependence of mobility curves for (a) Ga0.06In0.94 N and (b) Ga0.32In0.68 N.

Mentions: It is clear from Figure 2 that at low temperatures, electron mobilities in Ga0.06In0.94 N and Ga0.32In0.68 N are determined by alloy potential-induced scattering, interface roughness scattering and dislocation scattering mechanisms. Optical phonon scatterings become significant at high temperatures, as described above. Figure 3 shows experimental and calculated temperature-dependent mobility of the Ga0.52In0.48 N. The dislocation density increases with Ga concentration; therefore, its effect on the mobility becomes more pronounced in this sample. At low temperatures, mobility is limited by the same scattering mechanisms as in the other samples. At high temperatures, however, interface roughness and alloy potential restrict the mobility, but effect of the dislocation scattering becomes less dominant as a result of shortening Debye screening length due to higher carrier density. Furthermore, in the high-carrier-concentration regime, electron–phonon scattering is heavily screened, as described above and in references [19,25,29-33].


The role of dislocation-induced scattering in electronic transport in GaxIn1-xN alloys.

Donmez O, Gunes M, Erol A, Arikan CM, Balkan N, Schaff WJ - Nanoscale Res Lett (2012)

Experimental and calculated temperature dependence of mobility curves for (a) Ga0.06In0.94 N and (b) Ga0.32In0.68 N.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3526395&req=5

Figure 2: Experimental and calculated temperature dependence of mobility curves for (a) Ga0.06In0.94 N and (b) Ga0.32In0.68 N.
Mentions: It is clear from Figure 2 that at low temperatures, electron mobilities in Ga0.06In0.94 N and Ga0.32In0.68 N are determined by alloy potential-induced scattering, interface roughness scattering and dislocation scattering mechanisms. Optical phonon scatterings become significant at high temperatures, as described above. Figure 3 shows experimental and calculated temperature-dependent mobility of the Ga0.52In0.48 N. The dislocation density increases with Ga concentration; therefore, its effect on the mobility becomes more pronounced in this sample. At low temperatures, mobility is limited by the same scattering mechanisms as in the other samples. At high temperatures, however, interface roughness and alloy potential restrict the mobility, but effect of the dislocation scattering becomes less dominant as a result of shortening Debye screening length due to higher carrier density. Furthermore, in the high-carrier-concentration regime, electron–phonon scattering is heavily screened, as described above and in references [19,25,29-33].

Bottom Line: Hall effect measurements are performed at temperatures between 77 and 300 K.Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent.In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Science Faculty, Department of Physics, Istanbul University, Vezneciler, Istanbul 34134, Turkey. arikan@istanbul.edu.tr.

ABSTRACT
Electronic transport in unintentionally doped GaxIn1-xN alloys with various Ga concentrations (x = 0.06, 0.32 and 0.52) is studied. Hall effect measurements are performed at temperatures between 77 and 300 K. Temperature dependence of carrier mobility is analysed by an analytical formula based on two-dimensional degenerate statistics by taking into account all major scattering mechanisms for a two-dimensional electron gas confined in a triangular quantum well between GaxIn1-xN epilayer and GaN buffer. Experimental results show that as the Ga concentration increases, mobility not only decreases drastically but also becomes less temperature dependent. Carrier density is almost temperature independent and tends to increase with increasing Ga concentration. The weak temperature dependence of the mobility may be attributed to screening of polar optical phonon scattering at high temperatures by the high free carrier concentration, which is at the order of 1014 cm-2. In our analytical model, the dislocation density is used as an adjustable parameter for the best fit to the experimental results. Our results reveal that in the samples with lower Ga compositions and carrier concentrations, alloy and interface roughness scattering are the dominant scattering mechanisms at low temperatures, while at high temperatures, optical phonon scattering is the dominant mechanism. In the samples with higher Ga compositions and carrier concentrations, however, dislocation scattering becomes more significant and suppresses the effect of longitudinal optical phonon scattering at high temperatures, leading to an almost temperature-independent behaviour.

No MeSH data available.


Related in: MedlinePlus