Two-dimensional electron gas density in Al1−xInxN/AlN/GaN heterostructures (0.03≤x≤0.23)

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Compared to the AlGaN alloy, which can only be grown under tensile strain on GaN, the AlInN alloy is predicted by Vegard’s law to be lattice-matched (LM) on fully relaxed GaN templates for an indium content of ∼17.5%, i.e., it can be grown either tensely or compressively on GaN. The effect of strain on the polarization induced sheet charge density at the Al1−xInxN/AlN/GaN heterointerfaces is carefully investigated for 6 and 14 nm thick AlInN barriers including a 1 nm thick AlN interlayer. The barrier indium content ranges at 0.03≤x≤0.23 for 6 nm thick barriers and 0.07≤x≤0.21 for 14 nm thick barriers. It is found that the two-dimensional electron gas (2DEG) density varies between (3.5±0.1)×1013cm−2 and (2.2±0.1)×1013 cm−2 for 14 nm thick barriers. Finally, a 2DEG density up to (1.7±0.1)×1013 cm−2 is obtained for a nearly LM AlInN barrier with ∼14.5% indium on GaN as thin as 6 nm.