Nanoscale GaN Epilayer Grown by Atomic Layer Annealing and Epitaxy at Low Temperature

Abstract

Heteroepitaxy with large thermal and lattice mismatch between the semiconductor and substrate is a critical issue for high-quality epitaxial growth. Typically, high growth temperatures (>1000 °C) are required to achieve high-quality GaN epilayers by conventional metal−organic chemical vapor deposition. In this study, the high-quality GaN heteroepitaxy is realized by atomic layer annealing and epitaxy (ALAE) at a low growth temperature of 300 °C. The layer-by-layer, in situ He/Ar plasma treatment at a low plasma power was introduced in each cycle of atomic layer deposition to contribute the effective annealing effect for significant enhancement of the GaN crystal quality. The Penning effect is responsible for significant improvement of the GaN crystal quality due to the incorporation of He into the Ar plasma. The high-resolution transmission electron microscopy, nano-beam electron diffraction, and atomic force microscopy reveal a high-quality nanoscale single-crystal GaN heteroepitaxy and a very smooth surface. The full width at half-maximum of the X-ray rocking curve of the GaN epilayer is as low as 168 arcsec. The low-temperature ALAE technique is highly beneficial to grow high-quality nanoscale GaN epilayers for sustainable, energy-saving, and energy-efficient devices including high-performance solid-state lighting, solar cells, and highpower electronics.

Interfacial Tailoring for the Suppression of Impurities in GaN by In Situ Plasma Pretreatment via Atomic Layer Deposition

“…It is noteworthy that the plasma pretreatment leads to an increase of the binding energy of Ga−N from 19.3 to 19.4 eV, suggesting the film densification due to the in situ plasma pretreatment. 45 XRR was adopted to measure the density of the as-grown films. Figure 5a shows XRR curves of the nitridated and nonnitridated GaN films.…”

“…It can be seen that the value of n at 635 nm for nitridated GaN is 2.28, which is close to the value of the highquality GaN reported in literatures. 45 As a comparison, the non-nitridated GaN shows an n of 2.23 at 635 nm. The increase of n means higher density, which further verifies the results measured from XPS and XRR.…”

“…More NH 2 radical species generated on the surface after plasma pretreatment might contribute to a higher gallium content. It is noteworthy that the plasma pretreatment leads to an increase of the binding energy of Ga–N from 19.3 to 19.4 eV, suggesting the film densification due to the in situ plasma pretreatment …”

Enhancement of Dielectric Properties of Nanoscale HfO2 Thin Films Via Atomic Layer Bombardment

“…Nevertheless, the high-temperature annealing may give rise to uncontrollable diffusion of dopants and interfacial chemical reactions, which are unfavorable for the fabrication of nanoscale devices. In our previous study, an innovative concept of atomic layer annealing (ALA) or atomic layer bombardment (ALB) has been proposed. ,, The exposure of inert gas plasma in each ALD cycle was utilized in the ALA/ALB process as an alternative energy source, during which the ion bombardment provides energy to the surface of the as-deposited layer . The utilization of argon (Ar) or helium (He) inert gases in the plasma is to prevent the involvement of a chemical reaction.…”

“…The in situ layer-by-layer energy transfer from the plasma exposure leads to the elevation of surface temperature as well as the enhancement of surface reactions and adatom migration, which provide an additional route for tailoring the properties of thin films deposited by typical ALD processes. Accordingly, the ALA/ALB technique contributes to the amorphous-to-epitaxial phase transformation of AlN and GaN and the paraelectric-to-ferroelectric phase transition in nanoscale ZrO 2 thin films . However, it should be noticed that the energetic ion bombardment might induce bond breaking, displacement of atoms, and ion etching in as-deposited thin films .…”