In/GaN(0001)-(3×3)R30° adsorbate structure as a template for embedded (In, Ga)N/GaN monolayers and short-period superlattices

Abstract

We explore an alternative way to fabricate (In,Ga)N/GaN short-period superlattices on GaN(0001) by plasmaassisted molecular beam epitaxy. We exploit the existence of an In adsorbate structure manifesting itself by a ( √ 3 × √ 3)R30 • surface reconstruction observed in-situ by reflection high-energy electron diffraction. This In adlayer accommodates a maximum of 1/3 monolayer of In on the GaN surface and, under suitable conditions, can be embedded into GaN to form an In 0.33 Ga 0.67 N quantum sheet whose width is naturally limited to a single monolayer. Periodically inserting these quantum sheets, we synthesize (In,Ga)N/GaN short-period superlattices with abrupt interfaces and high periodicity as demonstrated by x-ray diffractometry and scanning transmission electron microscopy. The embedded quantum sheets are found to consist of single monolayers with an In content of 0.25-0.29. For a barrier thickness of 6 monolayers, the superlattice gives rise to a photoluminescence band at 3.16 eV, close to the theoretically predicted values for these structures.arXiv:1701.04680v1 [cond-mat.mtrl-sci]

Self‐Limiting Growth of Ultrathin GaN/AlN Quantum Wells for Highly Efficient Deep Ultraviolet Emitters

“…In fact, MBE growth of high-quality, ultrathin GaN (as well as InN) QWs has been demonstrated frequently. [18][19][20][21][22][23] However, MOVPE growth is quite rare, [16,22] despite its technological importance. In this study, we demonstrate self-limiting of the GaN thickness to the ML scale during MOVPE growth, facilitating the fabrication of highly reproducible ultrathin GaN QWs.…”

“…To fabricate such ultrathin GaN QWs embedded in Al(Ga)N, molecular beam epitaxy (MBE) appears to be better suited than metalorganic vapor phase epitaxy (MOVPE) because MBE can precisely control the thickness with the assistance of a reflection high‐energy electron diffraction technique. In fact, MBE growth of high‐quality, ultrathin GaN (as well as InN) QWs has been demonstrated frequently . However, MOVPE growth is quite rare, despite its technological importance.…”

Role of hole confinement in the recombination properties of InGaN quantum structures

“…A series of four SL samples each consisting of ten periods of polar InGaN QWs separated by GaN barriers of different thickness were grown by molecular beam epitaxy (MBE) at 550 °C 23 . Composition and thickness of the InGaN layers and the GaN barriers are quantified by TEM throughout the entire sample series.…”

“…Indeed, we have observed experimentally a strong decrease of the emission intensity for the 6 MLs thick barrier sample in PL measurements for different excitation and detection conditions. Thus, reducing the hole localization enhances their probability of reaching non-radiative recombination centers in the GaN barriers 23 . Since the GaN barriers were grown at 550 °C, optimized for achieving high In contents in the QWs, it is far below the optimum for GaN and, thus, results in a high number of point defects.…”

InN Quantum Dots by Metalorganic Chemical Vapor Deposition for Optoelectronic Applications

“…MOCVD studies of InN have largely focused on the growth of nanostructures such as quantum dots or dashes (QDs) due in part to the natural formation of these structures under large lattice mismatch conditions. Studies via molecular beam epitaxy (MBE) have shown evidence for stress driven surface reconstructions resulting in the formation of In 0.33 Ga 0.67 N instead of pure InN quantum wells in (0001) InN/GaN multi-layer structures (Suski et al, 2014;Chèze et al, 2017). Some MBE studies report monolayer-thick strained InN layers and, while these layers are useful for digital alloy applications (Yoshikawa et al, 2007;Yoshikawa et al, 2008;Gorczyca et al, 2018), they have limited usage in infrared optoelectronics, as their very thin nature typically leads to a blue shift resulting in emission in the visible range of the electromagnetic spectrum (Wu et al, 2009).…”