Overcoming the Miscibility Gap of GaN/InN in MBE Growth of Cubic In x Ga1–x N

• Published in: ACS applied materials & interfaces Vol. 15; no. 33; pp. 39513 - 39522
• Main Authors: Zscherp, Mario Fabian, Jentsch, Silas Aurel, Müller, Marius Johannes, Lider, Vitalii, Becker, Celina, Chen, Limei, Littmann, Mario, Meier, Falco, Beyer, Andreas, Hofmann, Detlev Michael, As, Donat Josef, Klar, Peter Jens, Volz, Kerstin, Chatterjee, Sangam, Schörmann, Jörg
• Format: Journal Article
• Language: English
• Published: American Chemical Society 23.08.2023
• Subjects: Functional Inorganic Materials and Devices; strain; molecular beam epitaxy; optical properties; miscibility; cubic III-nitrides; TEM; In x Ga1−x N
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.3c06319

The lack of internal polarization fields in cubic group-III nitrides makes them promising arsenic-free contenders for next-generation high-performance electronic and optoelectronic applications. In particular, cubic In x Ga1–x N semiconductor alloys promise band gap tuning across and beyond the visible spectrum, from the near-ultraviolet to the near-infrared. However, realization across the complete composition range has been deemed impossible due to a miscibility gap corresponding to the amber spectral range. In this study, we use plasma-assisted molecular beam epitaxy (PAMBE) to fabricate cubic In x Ga1–x N films on c-GaN/AlN/3C-SiC/Si template substrates that overcome this challenge by careful adjustment of the growth conditions, conclusively closing the miscibility gap. X-ray diffraction reveals the composition, phase purity, and strain properties of the In x Ga1–x N films. Scanning transmission electron microscopy reveals a CuPt-type ordering on the atomistic scale in highly alloyed films with x(In) ≈ 0.5. Layers with much lower and much higher indium content exhibit statistical distributions of the cations Ga and In. Notably, this CuPt-type ordering results in a spectrally narrower emission compared to that of statistically disordered zincblende materials. The emission energies of the films range from 3.24 to 0.69 eV and feature a quadratic bowing parameter of b = 2.4 eV. In contrast, the LO-like phonon modes that are observed by Raman spectroscopy exhibit a one-mode behavior and shift linearly from c-GaN to c-InN.