Epitaxial growth and interfaces of high-quality InN films grown on nitrided sapphire substrates

Abstract

InN films have been grown on sapphire substrates nitrided by N plasma with different durations by radio-frequency plasma assisted molecular beam epitaxy (RF-MBE). In-depth investigation reveals that AlN is generated on a sapphire surface during the nitridation, and 60 min nitridation helps in the formation of an ordered and flat AlN interlayer between the substrate and the InN film, which improves the surface migration of In atoms on the substrate, and consequently helps in obtaining a single-crystalline c-plane InN film of high quality with 1.0 Â 10 19 cm À3 carrier density and 1350 cm 2 /(VÁs) carrier mobility. Too short nitridation duration will result in a polycrystalline InN film, and too long nitridation duration will damage the surface quality of the newly generated AlN interlayer which consequently deteriorates the InN film quality. Control of the AlN interlayer quality plays a critical role in the growth of a high-quality InN epitaxial film on the sapphire substrate.

Coherent X-ray Spectroscopy Elucidates Nanoscale Dynamics of Plasma-Enhanced Thin-Film Growth

“…At the early growth times, the regions between mounds can be confidently described as sapphire with limited coverage of very small InN nuclei as the growth per cycle was approximately one tenth of a monolayer. Thus, the difference between the present result for growth on sapphire as compared to earlier work examining growth on GaN could be due to the different substratesadatom diffusion on the sapphire surface is generally slower than on GaN . The In diffusion length is also limited when there is a background of active nitrogen species.…”

“…Thus, the difference between the present result for growth on sapphire as compared to earlier work examining growth on GaN could be due to the different substrates�adatom diffusion on the sapphire surface is generally slower than on GaN. 51 The In diffusion length is also limited when there is a background of active nitrogen species. More detailed information about the continued early growth period comes from the TTCF at T = 420 s when there is sufficient intensity to measure the TTCF but regions of the bare substrate surface remain.…”

Nitridation effect of the α-Al2O3 substrates on the quality of the GaN films grown by pulsed laser deposition

“…We attribute these different results to the nitridation of a-Al 2 O 3 substrates, which leads to the formation of a thin AlN layer. [45][46][47] On the one hand, this AlN layer is good for the nucleation of GaN lms and enhances the migration of GaN precursors on surfaces. On the other hand, this AlN layer hampers the generation of the interfacial layer between GaN and a-Al 2 O 3 substrates.…”

Characterization of InN Grown Directly on Sapphire Substrate Using Plasma‐Enhanced Metal Organic Chemical Vapor Deposition

“…Figure a shows 2θ/ω scans of XRD from 28° to 44° of Sample C and Sample D. Both the samples exhibited two peaks at 2 θ = 31.3° and 41.5°, corresponding to InN $$( {0002} )$$ and Al 2 O 3 $$( {0006} )$$, respectively. [ 37 ] No peak regarding metallic In droplets (at 2 θ ≈33°) [ 21 ] was detected. The result matches the previous report that InN growth on a GaN/Al 2 O 3 template.…”

“…Secondly, a depth of ≈0.5 nm corresponds to the AlN thickness of 0.42 nm, as evaluated by spectroscopic ellipsometry (not shown).The InN samples, labeled as Sample C and Sample D, were grown under the same conditions without and with N 2 plasma irradiated Al 2 O 3 substrates. Figure3ashows 2𝜃/𝜔 scans of XRD from 28°to 44°of Sample C and Sample D. Both the samples exhibited two peaks at 2𝜃 = 31.3°and 41.5°, corresponding to InN (0002) and Al 2 O 3 (0006), respectively [37]. No peak regarding metallic In droplets (at 2𝜃 ≈33°)[21] was detected.…”