Epitaxial tilting of GaN grown on vicinal surfaces of sapphire

Abstract

Using the synchrotron Laue method and high-resolution x-ray diffraction, we have revealed the epitaxial tilting effect of gallium nitrite (GaN) films grown on vicinal (0001) surfaces of sapphire and their relationship to the offcut angles and the substrate surface steps. This effect is a consequence of the large outof-plane lattice mismatch between GaN and sapphire, and can be explained by an extended Nagai theory. The large lattice tilts and their formation mechanism indicate that the substrate surface morphology is an important factor that affects the epitaxy process and the crystalline quality of GaN films grown via vicinal-surface epitaxy.

Investigation of crystallographic tilting in GaSb/GaAs heteroepitaxial structure by high-resolution X-ray diffraction

“…For a lattice-mismatched heteroepitaxy on a stepped surface, the epilayer generally tilts with respect to the substrate [9][10][11]. But, to our knowledge, the tilt in GaSb/ GaAs heterosystem has not been reported in detail.…”

Nanoscale Electrostructural Characterization of Compositionally Graded AlxGa1–xN Heterostructures on GaN/Sapphire (0001) Substrate

“…This tilt between GaN and sapphire can be explained by the extended Nagai theory. 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 15 can lead to the lateral modulations of charge carriers and local fluctuations of surface potential along steps, which will be discussed below.…”

“…(20)(21)(22)(23)(24)(25) RSMs of graded Al x Ga 1-x N HS on GaN for samples G1 and G2. The inset illustrates the influence of lateral coherence length (L c ) and tilt (τ) on broadening the peak comparative to the diffraction vector (Q).…”

Hydride vapor phase epitaxy of GaN on the vicinal c-sapphire with a CrN interlayer

“…3, the surface becomes rough over a certain value of 0.51. In case of large off-angle, two adjacent steps can easily be merged into a higher step, and at relatively small off-angle, it is difficult to merge a couple of two steps with long-step spacing [12,13]. Such step bunches may cause the rough surface of GaN at relatively high off-angle.…”