The investigation of GaN growth on silicon and sapphire using in-situ time-of-flight low energy ion scattering and RHEED

• Published in: Journal of crystal growth 1996-07, Vol.164 (1), p.167-174
• Main Authors: Taferner, W.T., Bensaoula, A., Kim, E., Bousetta, A.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Molecular, atomic, ion, and chemical beam epitaxy; Physics
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(96)00020-6

In-situ time-of-flight low energy ion scattering (TOF-LEIS) and reflection high energy electron diffraction (RHEED) is used effectively to monitor surface structure, major elements, and impurities during substrate annealing, nitridation and thin film growth of GaN on Si and Al 2O 3 substrates by electron-cyclotron-resonance (ECR) assisted MBE. During the annealing process of silicon, a combination of time-of-flight direct recoil spectroscopy (TOF-DRS) and mass spectroscopy of recoiled ions (MSRI) was used to monitor the desorption of surface contaminants such as H, C, and O. A change from a 1 × 1 RHEED pattern of oxygen-covered Si(001) to a 1 × 2 + 2 × 1 RHEED pattern, evidence of a clean Si(001) substrate, was observed. For the case of Al 2O 3(0001), a 1 × 1 RHEED pattern of the hexagonal structure was seen when all major contaminants were removed, as indicated by MSRI. The nitridation of a clean Al 2O 3 surface was followed by RHEED and the formation of an AlN overlayer was confirmed by MSRI. A 1 × 1 RHEED pattern was observed after GaN thin film growth on sapphire, indicating a good crystalline structure. Si nitridation and subsequent deposition of columnar GaN on Si, resulted in an amorphous RHEED pattern. MSRI spectra showed the presence of Si in addition to Ga and N. When nitridation of Si was avoided the resulting GaN film was polycrystalline as observed by RHEED and complete coverage occurred, evidenced by the absence of Si in the MSRI spectra. The results show that a combination of RHEED and TOF-LEIS permit real-time optimization of substrate preparation and thin film growth parameters.