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

Abstract

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 ͑LM͒ on fully relaxed GaN templates for an indium content of ϳ17.5%, 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 Al 1−x In x N / 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 0.03Յ x Յ 0.23 for 6 nm thick barriers and 0.07Յ x Յ 0.21 for 14 nm thick barriers. It is found that the two-dimensional electron gas ͑2DEG͒ density varies between ͑3.5Ϯ 0.1͒ ϫ 10 13 cm −2 and ͑2.2Ϯ 0.1͒ ϫ 10 13 cm −2 for 14 nm thick barriers. Finally, a 2DEG density up to ͑1.7Ϯ 0.1͒ ϫ 10 13 cm −2 is obtained for a nearly LM AlInN barrier with ϳ14.5% indium on GaN as thin as 6 nm.

Enhancement and Narrowing of Excitonic Lines in AlInN/GaN Heterostructures

“…The positive polarization charge at the interface is responsible for the tendency to collect the free electrons from other sources [20]. The sources of free electrons can be either surface states [20][21][22][23] and/or the AlInN layer [18]. For example, a typical AlInN layer contains a free electron concentration of (1-5) × 10 18 cm −3 , possibly due to nitrogen vacancies acting as shallow donors or residual oxygen impurities [18].…”

Measurement of valence-band offsets of InAlN/GaN heterostructures grown by metal-organic vapor phase epitaxy

“…3͑a͒. 7 This difference in polarization at the heterointerface produces positive interface charge. range of probing depths and observed surface potentials that will be described later, while the nonuniform electric fields were calculated for GaN layers.…”

“…Similar results have previously been reported. [6][7][8] In XPS measurement, only shallow parts of InAlN layers were probed as shown in Fig. 3͑b͒ for the samples with thick InAlN layers with 2DEG, resulting in no detection of the Ga 3d spectrum from the host GaN layer.…”

Luminescence from two-dimensional electron gases in InAlN/GaN heterostructures with different In content

“…10 Regardless of the final application, investigations on both the electrical and optical properties of the 2DEG are crucial for understanding the intrinsic properties of the InAlN/GaN heterostructures, which is the bottleneck to advance the nitride electronics technology. Up to now, InAlN/GaN HS have been studied widely by electrical measurements, 5,11 however, there is still a lack of systematic studies concerning optical characterization.…”

“…In x Al 1Àx N/GaN heterostructures (HSs), in particular for the lattice-matched composition x % 0.18, have emerged recently as promising candidates for next-generation electronic devices in millimeter-and submillimeter-wave applications 1,2 as well as for the improvement of optoelectronic devices. 3,4 The use of InAlN layers offers several attractive advantages, such as a strong spontaneous polarization that induces an extremely high sheet carrier charge density in the two-dimensional-electron-gas (2DEG) (about 3.5 Â 10 13 cm À2 for 14 nm thick Al 0.93 In 0.07 N barriers), 5,6 and a strain-free heterojunction that could reduce structural defects caused by the lattice mismatch. 7,8 Moreover, due to their relatively high difference in refractive indices and the possibility of lattice matching, InAlN/GaN multilayer stacks with quarter-wave layers are a very promising approach for distributed Bragg mirrors 9 and its application in nitride microcavity light-emitting diodes.…”