Effect of thermal annealing and nitrogen composition on quantum transport in GaInNAs alloy based modulation doped quantum well structures
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Effect of thermal annealing on quantum transport properties have been investigated on as-grown and annealed n-type modulation doped GaInNAs/GaAs quantum well (QW) structures with various nitrogen concentration in low (B < 0.1 T) and high magnetic field (up to 18 T) regions between 75 mK and 1 K. We have observed pronounced plateaus in quantum Hall effect results. The shape of the plateaus do not have a temperature-dependent characteristic for both as-grown and annealed samples. On the other hand, because electron mobility decreases with increasing nitrogen concentration and enhances upon annealing process, the plateaus have more flattened characteristic. The temperature-dependent low field magnetoresistance measurements reveal that the samples exhibit weak antilocalization, which is affected from nitrogen concentration and thermal annealing. Electronic transport parameters such as spin coherence, phase coherence and elastic scattering times, Rashba parameter and spin-splitting energy are extracted from low field magnetoconductivity plots. It is shown that dilute amount of nitrogen composition is an important parameter, which affects the strength of the spin-orbit interaction due to the strongly localized electron states and disorder-induced electron momentum scattering. The longest spin relaxation time is observed for the sample with the highest nitrogen composition and the lowest electron mobility. The calculated Rashba parameter, spin-orbit splitting energy and spin relaxation time for as-grown and annealed samples reveal that thermal annealing causes a decrement in these parameters, but increasing nitrogen composition leads to an increase in spin relaxation time. Therefore both nitrogen composition and thermal annealing can be used to manipulate the spin-orbit coupling strength in GaInNAs-based modulation doped QW structures. (C) 2016 Elsevier B.V. All rights reserved.
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