Investigation of InAlN Layers Surface Reactivity after Thermal Annealings: A Complete XPS Study for HEMT

Abstract

The surface chemistry of InAlN ultra-thin layers, having undergone an oxidation procedure usually running through the HEMT fabrication process (850 • C, O 2 and O 2 +Ar) is studied by XPS. The suitability of XPS analysis to operate as a retro-engineering tool for added value microelectronic devices fabrication is shown. A precise examination of the Al2p, In3d 5/2 , N1s, and O1s peaks directly informs about spatial and atomic arrangement. The formation of a covering 3 nm surface oxide is evidenced after O 2 annealing. Once annealed, two specific additional N1s contributions are shown, at higher (404.0 eV) and lower binding energies (397.4 eV) compared to the InAlN matrix one (396.5 eV). To our knowledge, such fingerprint is rather unusual for ternary III-V materials. It reveals the formation of a nitrogen deficient interlayer, situated between the oxide overlayer and the undisturbed matrix, and the presence of interstitial N 2 molecules trapped at the interface. After Ar annealing, both oxide and interface layers are partially reorganized. InAlN reactivity toward higher annealing temperature (950 • C) and its stability over time is finally discussed. N 2 molecules are unstable and progressively eliminated in time although nitrogen deficient interlayer still remains. Thermal treatments below 850 • C are recommended to preserve the barrier chemical integrity.

In‐depth analysis of InAlN/GaN HEMT heterostructure after annealing using angle‐resolved X‐ray photoelectron spectroscopy

“…As mentioned in the experimental section, in order to make high‐performing HEMT devices, In 0.2 Al 0.8 N (InAlN) barrier layer is posttreated with a deoxidation step (NH 4 OH soaking) followed by a controlled oxidation (annealing under O 2 partial pressure, 850°C), which governs the surface oxidation state. In a previous work, the influence of additional Ar annealing and time evolution has been evaluated and enabled us to get a better understanding of the overall chemical evolution of the InAlN barrier after such O 2 thermal treatment 8 . On the basis of XPS analyses, we evidenced that a reorganization within the layer occurs after annealing.…”

“…Figure 3A shows the N1s photopeak evolution with the photoelectron take‐off angle, θ. Three distinct chemical environments are highlighted here, as previously described 8 and reported in other works on binary compounds 9,10 . The main component at 397.4 eV, “N1s (mat),” corresponds to the undisturbed InAlN matrix and is used as a reference for intensity normalization.…”

“…In a previous paper, we demonstrated that proceeding to the postannealing under O 2 partial pressure induces reproducible modifications. We evidenced the generation of nitrogen defects that can be seen as a In y Al (1‐y) N <1 interlayer supposed to be localized between the surface oxide and the InAlN matrix, as well as the presence of N 2 molecules embedded inside this structure 8 . However, the exact spatial organization of the N 2 molecules and the interlayer remained an open question that has to be clarified.…”

“…interlayer supposed to be localized between the surface oxide and the InAlN matrix, as well as the presence of N 2 molecules embedded inside this structure. 8 However, the exact spatial organization of the N 2 molecules and the interlayer remained an open question that has to be clarified.…”

Effect of Gas Annealing on the Electrical Properties of Ni/AlN/SiC

“…When it reducing the relative nitrogen content, AlN chemical bonds break up. This is likely due to the result of the oxidation of the AlN surface barrier that is presumed to occur [ 28 ]; also, annealing has related to the creation of nitrogen defects in the form of interstitial N 2 trapped between the surface oxide film and AlN film interlayer. Figure 5 b shows the measured XPS core-level O 1s spectra.…”