Highly Homogeneous 2D/3D Heterojunction Diodes by Pulsed Laser Deposition of MoS₂ on Ion Implantation Doped 4H‐SiC

Abstract

such as the thickness-dependent bandgap, which are attractive for ultra-scaled digital electronics beyond silicon, optoelectronics, and energy applications. [1] The danglingbond free structure of TMDs offers the unique possibility of realizing high-quality van der Waals heterostructures with bulk semiconductors for the implementation of advanced heterojunction devices exploiting current transport at the interface. [2][3][4][5] In particular, the integration of single or few layers MoS 2 with wide bandgap semiconductors, such as the group-III Nitrides (GaN, AlN, and AlGaN alloys) and 4H-SiC, is currently the object of increasing interest in optoelectronics (e.g., for the realization of high responsivity dual-band photo detectors covering the spectral ranges of visible and ultraviolet), [6][7][8][9][10][11] and in electronics (e.g., for the realization of heterojunction diodes, including band-toband tunnel diodes). [12][13][14][15][16][17] Motivated by these interests, different approaches have been employed to fabricate such heterojunction devices, including the transfer of MoS 2 flakes exfoliated from bulk crystals [6,9,10] or grown on foreign substrates, [12,13,18] and the direct deposition of MoS 2 on GaN [14][15][16] or 4H-SiC. [11,17] In particular, nearly unstrained and highly oriented monolayer MoS 2 triangular domains on the GaN( 0001) basal plane have been In this paper, 2D/3D heterojunction diodes have been fabricated by pulsed laser deposition (PLD) of MoS 2 on 4H-SiC(0001) surfaces with different doping levels, i.e., n − epitaxial doping (≈10 16 cm −3 ) and n + ion implantation doping (>10 19 cm −3 ). After assessing the excellent thickness uniformity (≈3L-MoS 2 ) and conformal coverage of the PLD-grown films by Raman mapping and transmission electron microscopy, the current injection across the heterojunctions is investigated by temperature-dependent current-voltage characterization of the diodes and by nanoscale current mapping with conductive atomic force microscopy. A wide tunability of the transport properties is shown by the SiC surface doping, with highly rectifying behavior for the MoS 2 /n − SiC junction and a strongly enhanced current injection for MoS 2 /n + SiC one. Thermionic emission is found the dominant mechanism ruling forward current in MoS 2 /n − SiC diodes, with an effective barrier Φ B = (1.04 ± 0.09) eV. Instead, the significantly lower effective barrier Φ B = (0.31 ± 0.01) eV and a temperature-dependent ideality factor for MoS 2 /n + SiC junctions is explained by thermionic-field-emission through the thin depletion region of n + doped SiC. The scalability of PLD MoS 2 deposition and the electronic transport tunability by implantation doping of SiC represents key steps for industrial development of MoS 2 /SiC devices.

Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D β-Ga2O3

“…3 with values reported in the literature for diodes and p-n junctions. 35,36,[56][57][58][59][60][61][62] The WS 2 (001), WSe 2 (−201) and BP (−201) ratios are among the lowest recorded for Ga 2 O 3 -based 2D/3D diodes.…”

Interface Structure and Doping of Chemical Vapor Deposition‐Grown MoS2 on 4H–SiC by Microscopic Analyses and Ab Initio Calculations

“…demonstrating advanced photodetectors operating both in the visible and in the ultraviolet (UV) spectral range [10][11][12][13] and innovative heterojunction diodes for fast switching and low-power consumption electronics. [14][15][16][17][18] The hexagonal structure of 4H-SiC and GaN and the very low lattice mismatch with MoS 2 on the basal plane (%2.9% in the case of 4H-SiC and < 1% in the case of GaN) favor the direct epitaxial growth of MoS 2 layers on these substrates. The nucleation and growth of highly oriented and nearly unstrained triangular MoS 2 domains are obtained on the GaN(0001) basal plane by chemical vapor deposition (CVD) at temperatures of 700-800 °C.…”

“…[ 8,9 ] In this context, significant research efforts have been recently directed on the integration of the MoS 2 with wide‐bandgap (WBG) semiconductors, such as silicon carbide (4H‐ and 6H–SiC), gallium nitride (GaN), and related group‐III nitrides (AlN and AlGaN alloys), with the aim of demonstrating advanced photodetectors operating both in the visible and in the ultraviolet (UV) spectral range [ 10–13 ] and innovative heterojunction diodes for fast switching and low‐power consumption electronics. [ 14–18 ] The hexagonal structure of 4H–SiC and GaN and the very low lattice mismatch with MoS 2 on the basal plane (≈2.9% in the case of 4H–SiC and < 1% in the case of GaN) favor the direct epitaxial growth of MoS 2 layers on these substrates. The nucleation and growth of highly oriented and nearly unstrained triangular MoS 2 domains are obtained on the GaN(0001) basal plane by chemical vapor deposition (CVD) at temperatures of 700–800 °C.…”

Integrating 2D layered materials with 3D bulk materials as van der Waals heterostructures for photodetections: Current status and perspectives

“…For instance, by directly growing MoTe 2 on Si substrate, Lu et al fabricated a MoTe 2 /Si vertical 2D/3D heterojunction photodiode with the response range spanning from 300 to 1800 nm. Most recently, MoS 2 /4H‐SiC heterojunction diodes have been fabricated via PLD deposition of MoS 2 on 4H‐SiC surfaces 45 . Impressively, this structure showed an electronic transport tunability by controlling the doping level of SiC, which paves the path for industrial development of MoS 2 /SiC device.…”

“…(iii) Pulsed laser deposition (PLD). On the right, cross‐sectional HRTEM image of MoS 2 on n + implanted 4H‐SiC by PLD; Reproduced with permission 45 . Copyright 2022, John Wiley and Sons.…”