Improvements in structural and optical properties of wafer-scale hexagonal boron nitride film by post-growth annealing

Abstract

Remarkable improvements in both structural and optical properties of wafer-scale hexagonal boron nitride (h-BN) films grown by metal-organic chemical vapor deposition (MOCVD) enabled by high-temperature post-growth annealing is presented. The enhanced crystallinity and homogeneity of the MOCVD-grown h-BN films grown at 1050 °C is attributed to the solid-state atomic rearrangement during the thermal annealing at 1600 °C. In addition, the appearance of the photoluminescence by excitonic transitions as well as enlarged optical band gap were observed for the post-annealed h-BN films as direct consequences of the microstructural improvement. The post-growth annealing is a very promising strategy to overcome limited crystallinity of h-BN films grown by typical MOCVD systems while maintaining their advantage of multiple wafer scalability for practical applications towards two-dimensional electronics and optoelectronics.

Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications

“…Therefore, to elucidate the chemical states at the heterointerface between few-layer h-BN and AlGaN, experimental observations and calculations of N K edge absorption spectra and the electronic structure calculation of pDOS were conducted for bare AlGaN, h-BN grown on AlGaN, and a MOCVD-grown h-BN sample as a reference, which is previously reported (Figure 3). 36 Figure 3a shows the schematics of the NEXAFS measurement and the atomic structures of the bare AlGaN HEMT (sample A), h-BN reference (sample B), and h-BN on the AlGaN/GaN HEMT (sample C). Because the NEXAFS spectrum involves an optical transition within an electron escape depth of about few nm from the surface, only atomic structures near the surface were considered.…”

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer‐Scale Growth and Beyond

“…For example, the layer number of multilayer graphene was identified by analyzing the relationship between the thickness and the full width at half maximum (FWHM) of the (002) peak in their X‐ray diffraction spectra. [ 94 ] The structural properties including the thickness and surface roughness of graphene, [ 95 ] WS 2 , [ 96 ] and h‐BN [ 97 ] were probed by investigating the X‐ray reflectivity. Although X‐rays based techniques are useful tools for identifying the layer number of 2D materials, fitting procedures are still needed; therefore, it must be noted that the fitting parameters should be carefully addressed to obtain the correct results when using such techniques.…”

Boron nitride for excitonics, nano photonics, and quantum technologies

“…Growth of bulk hBN crystals is realized after solidification of a melt of precursors ( [16][17][18]123] and refs therein) and their sizes are critically depending on the tricks under the technology used to cool down the melt in order to trigger and control as much as possible its solidification [124]. In epitaxial approaches of the growth, the boron nitride is (with hopefully good stoichiometry) deposited on a target substrate which can be a metal like gold [124], copper [125][126][127], or sapphire [128,129] or Highly Ordered Pyrolitic Graphite [40] or the Si face of SiC [130] to cite a few examples. The critical issues are the low growth rate, the need to operate the growth at high temperature, to control the coalescence of here and there germinated hBN nanocrystals [132] … .…”