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Improving the energy conversion efficiency of light-emitting diodes (LEDs) for blue light emission has been a continuing pursuit for the past several decades. Here, we report InGaN/GaN LEDs with improved energy efficiency through the simple deposition of multifunctional ultrathin AlN/Al 2 O 3 layers on top of p-type GaN (i.e., GaN:Mg) using remote plasma pretreatment and plasma-enhanced atomic-layer deposition (PEALD). The AlN/Al 2 O 3 stacked layers played principal roles in improving the LED energy efficiency: 1) The surface defect states of p-type GaN were reduced to minimize leakage current and oxidation was prevented by passivating the GaN surface; 2) the net positive charges formed at the AlN/GaN interface enhanced the hole injection rate into the multi-quantum well (MQW) by formation of downward band bending with the increased surface potential; and 3) the increased hole injection rate induced the band-filling effect and screening of internal polarization fields in the MQW. The AlN/Al 2 O 3 stacked layers deposited on the GaN:Mg have overall improved the radiative recombination rate of the InGaN/GaN LEDs and thus light-emission efficiency. X-ray photoelectron spectroscopy was used to characterize the surface potential change of GaN. The peak efficiency values of wall-plug efficiency, the external-quantum efficiency, and the efficacy of the AlN/Al 2 O 3 coated InGaN/GaN LEDs were improved by 29%, 29%, and 30%, respectively. The corresponding efficiency droop rates were decreased by 13%, 6% and 3%, respectively, as compared to those of reference LEDs. [ABSTRACT FROM AUTHOR]

β -Ga 2 O 3 , known as a next-generation wide-bandgap transparent semiconducting oxide (TSO), has considerable application potential in ultra-high-power and high-temperature devices. However, fabricating a smooth β -Ga 2 O 3 substrate is challenging owing to its strong mechanical strength and chemical stability. In this study, an atomic-scale smoothing method named plasma-enabled atomic-scale reconstruction (PEAR) is proposed. We find that three reconstruction modes, namely, 2D-island, step-flow, and step-bunching, can be identified with the increase in the input power; only the step-flow mode can result in the formation of an atomically smooth β -Ga 2 O 3 surface (S a = 0.098 nm). Various surface and subsurface characterizations indicate that the smooth β -Ga 2 O 3 surface shows excellent surface integrity, high crystalline quality, and remarkable photoelectric properties. The atomic-scale density functional theory-based calculations show that the diffusion energy barrier of a Ga atom is only 0.46 eV, thereby supporting the atomic mass migration induced by high-energy plasma irradiation in the experiment. Nanoscale molecular dynamics simulations reveal that O atoms firstly migrate to crystallization sites, followed by Ga atoms with a lower migration rate; reconstruction mainly proceeds along the <010> direction and then expands along the <100> and <001> directions. The millimeter-scale numerical simulations based on the finite element method demonstrate that the coupling of the thermal and flow fields of plasma is the impetus for PEAR of β -Ga 2 O 3. Furthermore, the smoothing generality of PEAR is demonstrated by extending it to other common TSOs (α -Al 2 O 3 , ZnO, and MgO). As a typical plasma-based atomic-scale smoothing method, PEAR is expected to enrich the theoretical and technological knowledge on atomic-scale manufacturing. [Display omitted] • Plasma-enabled atomic-scale reconstruction (PEAR) is developed to polish β -Ga 2 O 3. • The coupled thermal and flow fields are the impetus for atoms' mass reconstruction. • The reconstruction features of β -Ga 2 O 3 are revealed by multi-scale simulations. • The surface and subsurface quality of oxides can be greatly improved via PEAR. • PEAR shows excellent polishing generality for common semiconducting oxides. [ABSTRACT FROM AUTHOR]

We present evidence of homogenization of atomic diffusion properties caused by C and N interstitials in an equiatomic single-phase high entropy alloy (FeMnNiCoCr). This phenomenon is manifested by an unexpected interstitial-induced reduction and narrowing of the directly experimentally determined migration barrier distribution of mono-vacancy defects introduced by particle irradiation. Our observation by positron annihilation spectroscopy is explained by state-of-the-art theoretical calculations that predict preferential localization of C/N interstitials in regions rich in Mn and Cr, leading to a narrowing and reduction of the mono-vacancy size distribution in the random alloy. This phenomenon is likely to have a significant impact on the mechanical behavior under irradiation, as the local variations in elemental motion have a profound effect on the solute strengthening in high entropy alloys. [Display omitted] [ABSTRACT FROM AUTHOR]