Hydride CVD Hetero-epitaxy of B12P2 on 4H-SiC

Abstract

Icosahedral boron phosphide (B 12 P 2) is a wide bandgap semiconductor (3.35 eV) that has been reported to "selfheal" from high-energy electron bombardment, making it attractive for potential use in radioisotope batteries, radiation detection, or in electronics in high radiation environments. This study focused on improving B 12 P 2 hetero-epitaxial films by growing on 4H-SiC substrates over the temperature range of 1250-1450 • C using B 2 H 6 and PH 3 precursors in a H 2 carrier gas. XRD scans and Laue transmission photographs revealed that the epitaxial relationship was (0001) 1120 B 12 P 2 (0001) 1120 4H-SiC. The film morphology and crystallinity were investigated as a function of growth temperature and growth time. At 1250 • C, films tended to form rough, polycrystalline layers, but at 1300 and 1350 • C, films were continuous and comparatively smooth (R RMS ≤ 7 nm). At 1400 or 1450 • C, the films grew in islands that coalesced as the films became thicker. Using XRD rocking curves to evaluate the crystal quality, 1300 • C was the optimum growth temperature tested. At 1300 • C, the rocking curve FWHM decreased with increasing film thickness from 1494 arcsec for a 1.1 μm thick film to 954 arcsec for a 2.7 μm thick film, suggesting a reduction in defects with thickness.

Detection of defect populations in superhard semiconductor boron subphosphide B12P2 through X-ray absorption spectroscopy

“…Multiple samples of B 12 P 2 were grown on 4H-SiC substrates miscut 4 • to the (1100), in a cold-walled, inductively heated chemical vapor deposition (CVD) reactor. A detailed description of the deposition setup and deposition procedure under comparable conditions can be found elsewhere 26 . The substrates were placed in a TaCcoated graphite susceptor, where they were heated and etched in a H 2 carrier gas for 20 min.…”

“…This is consistent with the notion that the likelihood of regions of the crystal growing with imperfections in the long range crystalline order, increases for decreasing deposition temperatures. The employed deposition temperatures in this work are all below 1300 K, which is currently understood to be optimal for B 12 P 2 crystal growth 26 .…”

Ductility in Crystalline Boron Subphosphide (B12P2) for Large Strain Indentation

“…Although B 12 P 2 has potential important applications, the techniques of growing high-quality crystals are still in the early stages . Thus, the poor quality of current materials has limited its detailed characterization.…”

Suppression of Rotational Twins in Epitaxial B12P2 on 4H-SiC

“…B 12 P 2 films were deposited by CVD on 4H-SiC substrates miscut 4°t oward either the [112̅ 0] or the [11̅ 00] at 1300 °C for 30 min using the process described in our previous publication. 12 The films had a nominal thickness of 2 μm. These two miscuts were chosen because substrates miscut to the [112̅ 0] are the industry standard substrates for 4H-SiC homoepitaxy, while substrates miscut 7°to the [11̅ 00] suppress twinning in B 12 As 2 epitaxy.…”

“…In this work, B 12 P 2 was grown on (0001) 4H-SiC substrates miscut 4°to the [11̅ 00] and on substrates miscut 4°to the [112̅ 0] under the optimized conditions described in an earlier publication. 12 An idealized etch model as postulated by Zhang et al 18,25 is presented in detail to explain how the step morphology of the substrates evolves during an in situ H 2 etch and to describe how B 12 P 2 twins nucleate on the substrate surfaces. By selecting the miscut to be toward the [11̅ 00], the surface morphology can be engineered to suppress rotational twin formation during epitaxy.…”