Epitaxy of Hexagonal Boron Nitride Thin Films on Sapphire for Optoelectronics

Abstract

Recently, wide band gap hexagonal boron nitride (h-BN) has drawn considerable attention because of its superior properties and potential for optoelectronics applications. However, extremely high substrate temperatures are usually required to obtain highly crystalline h-BN films on dielectric substrates, which is highly desired for most electronic device applications. In this work, wafer-scale high-crystalline-quality h-BN films have been obtained via high-temperature annealing on PLD-grown amorphous BN films. It is found that the annealed h-BN film is epitaxially grown on sapphire with an orientation relationship: h-BN (0001)[11̅00]//sapphire (0001)[11̅00]. The narrow Raman peak and XRD rocking curve, as well as the observed strong excitonic emission, indicate the high crystalline quality of our epitaxial h-BN films. Moreover, the photodetectors fabricated from the annealed h-BN films exhibit an excellent device performance, suggesting that high-temperature annealing is a simple and promising strategy to obtain highly crystalline h-BN films for optoelectronic device applications.

High-Crystallinity and High-Temperature Stability of the Hexagonal Boron Nitride Film Grown on Sapphire

“…The thickness of hBN on sapphire can reach 5−10 nm by the chemical vapor deposition method. 35 However, more evidence is needed to confirm the crystallinity, uniformity, and continuity of the hBN film on sapphire. Controlling the thickness and surface morphology of hBN film precisely is still a challenge.…”

“…Controlling the thickness and surface morphology of hBN film precisely is still a challenge. Another advantage of using such a hBN-coated sapphire substrate is that it simplifies the fabrication of optoelectronic devices directly, as it is unnecessary to remove the sapphire substrate before device fabrication, so the hBN-coated sapphire makes it easier to fabricate all-transparent optoelectronic devices. , According to the catalysis-free sapphire, hyperactive parasitic gas-phase reactions and a self-terminating effect occurred during metal–organic chemical vapor deposition (MOCVD). The limitation of growth rate and the carbon impurities doping in hBN are known to be two of the most common defects in MOCVD. − The LPCVD method with NH 3 BH 3 as the precursor epitaxy of hBN is free from parasitic reactions and carbon-doped phenomena, facilitating the growth of various thicknesses of dope-free hBN film on sapphire substrates.…”

“…hBN on sapphire substrate has been achieved in some works ,, with a relatively low crystallinity. The thickness of hBN on sapphire can reach 5–10 nm by the chemical vapor deposition method . However, more evidence is needed to confirm the crystallinity, uniformity, and continuity of the hBN film on sapphire.…”

“…Another advantage of using such a hBN-coated sapphire substrate is that it simplifies the fabrication of optoelectronic devices directly, as it is unnecessary to remove the sapphire substrate before device fabrication, so the hBN-coated sapphire makes it easier to fabricate all-transparent optoelectronic devices. 12,35 According to the catalysis-free sapphire, hyperactive parasitic gas-phase reactions and a self-terminating effect occurred during metal−organic chemical vapor deposition (MOCVD). The limitation of growth rate and the carbon impurities doping in hBN are known to be two of the most common defects in MOCVD.…”

Hexagonal Boron Nitride Thick Film Grown on a Sapphire Substrate via Low-Pressure Chemical Vapor Deposition

“…If the isotope h- 10 BN is used, it will be one of the most promising potential future semiconductor neutron-detecting materials to replace 3 He gas neutron detectors. Current methods for h-BN film preparation mainly include mechanical stripping, liquid phase stripping, chemical vapor deposition (CVD), − and physical vapor deposition. , It is worth mentioning that the CVD method has unique advantages and potential for thin film growth due to simple equipment, ease of operation, and low cost. The basis of the CVD method for synthesizing BN films is the decomposition of compounds containing B and N, followed by their reaction on a substrate.…”