A study on Ga Si interdiffusion during (Al)GaN/AlN growth on Si by plasma assisted molecular beam epitaxy

Van der Waals Epitaxy of c-Oriented Wurtzite AlGaN on Polycrystalline Mo Substrates for Enhanced Heat Dissipation

“…4−8 The nontoxicity of AlGaN and miniaturization and stability of deep-UV diodes compared with traditional mercury lamps further promote demands and advances for AlGaN-related materials. 9 Due to the absence of homoepitaxial substrates, heteroepitaxial substrates including sapphire, 10−12 silicon carbide, 13 and silicon 14,15 are currently applied for AlGaN growth. In addition to the lattice mismatch and thermal expansion coefficient difference between the epilayers and heteroepitaxial substrates, the widely used sapphire also exhibits the drawbacks of mechanical inflexibility, electrical insulation, and poor thermal conductivity (around 2 W•K −1 •m −1 for Al 2 O 3 on sapphire at 200 °C), 16 which prevent the possible application of AlGaN in flexible optoelectronic devices with high efficiency and heat dissipation ability.…”

“…The ternary alloy of III-nitrides, AlGaN, possesses large and adjustable direct band gaps ranging from 3.4 to 6.2 eV, and thus it becomes a promising material for detection and luminescence devices working in the ultraviolet (UV) wavelength. − Peculiarly, the ability of killing most germs and viruses of AlGaN-based deep-UV diodes attracts increasing attention toward this material since the pandemic of COVID-19. − The nontoxicity of AlGaN and miniaturization and stability of deep-UV diodes compared with traditional mercury lamps further promote demands and advances for AlGaN-related materials . Due to the absence of homoepitaxial substrates, heteroepitaxial substrates including sapphire, − silicon carbide, and silicon , are currently applied for AlGaN growth. In addition to the lattice mismatch and thermal expansion coefficient difference between the epilayers and heteroepitaxial substrates, the widely used sapphire also exhibits the drawbacks of mechanical inflexibility, electrical insulation, and poor thermal conductivity (around 2 W·K –1 ·m –1 for Al 2 O 3 on sapphire at 200 °C), which prevent the possible application of AlGaN in flexible optoelectronic devices with high efficiency and heat dissipation ability.…”

Ga interaction with ZnO surfaces: Diffusion and melt-back etching

“…Combining ex-situ and in-situ analyses, we are able to extract the diffusion length of Ga in ZnO whiskers. On top of that, we reveal a mechanism behind the formation of etch pits on the ZnO surface, which is strikingly similar to melt-back etching of silicon by gallium [11,12].…”

“…4a) clearly revealed that the etch-pit formation is related to Ga droplets, which locally etch the ZnO surface. Such an effect, called melt-back etching, is well known from GaN epitaxy on silicon, where excess Ga causes etching of the silicon substrate [11,12]. For that particular material system, the mechanism remains not fully revealed yet.…”

2DEG enhancement via epilayer stress engineering in AlN/GaN/AlN heterostructure

“…Al has much more wetting tendency on Si than Ga, which makes the formation of AlN on Si or SiC easier than GaN [85]. Furthermore, GaN growths on Si and SiC suffer from the issues of SixNx formation, melt-back etching, Ga-Si interdiffusion and subsequent alloy formation [86]. The AlN nucleation layer prevents the formation of amorphous SixNx owing to the better Al-N bond formation than the Si-N bond [87].…”