Thermally Annealed GaN Nucleation Layers And The MOCVD Growth Of Si-Doped GaN Films On (00.1) Sapphire

Abstract

ABSTRACTThe effect of epitaxial growth temperature in the range 985 – 1050°C on the preparation of device quality Si-doped GaN layers on self-nucleated (00.1) sapphire has been explored. Not unexpectedly, several device-related properties monotonically improve with increasing growth temperature, including: (a) carrier density; and, (b) volume fraction of heteroepitaxial domains. However, a number of equally important device-related properties show a local maximum or minimum and include: (a) optical second-harmonic generation intensity; (b) structural coherence; and, particularly (c) surface morphology. The antecedents of the first class is found in an increase in surface and bulk diffusion and a reduction in film defect incorporation and stress at the GaN/GaN (nucleation layer)/α-Al2O3 heterointerface (even for overlays with thicknesses near 1 μm). The second class apparently stems from the limited range over which the thermally annealed GaN nucleation layer stimulates pseudo two-dimensional growth of the overlayer.