Electric dipole effect in PdCoO ₂ /β-Ga ₂ O ₃ Schottky diodes for high-temperature operation

Abstract

High-temperature operation of semiconductor devices is widely demanded for switching/sensing purposes in automobiles, plants, and aerospace applications. As alternatives to conventional Si-based Schottky diodes usable only at 200°C or less, Schottky interfaces based on wide-bandgap semiconductors have been extensively studied to realize a large Schottky barrier height that makes high-temperature operation possible. Here, we report a unique crystalline Schottky interface composed of a wide-gap semiconductor β-Ga2O3 and a layered metal PdCoO2. At the thermally stable all-oxide interface, the polar layered structure of PdCoO2 generates electric dipoles, realizing a large Schottky barrier height of ~1.8 eV, well beyond the 0.7 eV expected from the basal Schottky-Mott relation. Because of the naturally formed homogeneous electric dipoles, this junction achieved current rectification with a large on/off ratio approaching 108 even at a high temperature of 350°C. The exceptional performance of the PdCoO2/β-Ga2O3 Schottky diodes makes power/sensing devices possible for extreme environments.

High Performance β‐Ga2O3 Schottky Barrier Transistors with Large Work Function TMD Gate of NbS2 and TaS2

“…Until recent years, β-Ga 2 O 3 has been attracting quite an attention from researchers, due to its promising semiconducting properties: temperature stability, optical transparencies, or photostability due to large energy bandgap, high breakdown electric (E)-field, and minimum leakage current. [1][2][3][4][5][6][7][8][9] Gallium trioxide is basically known to have five different polymorphisms, α, β, γ, δ, and ε. [10,11] Of these modifications monoclinic β-Ga 2 O 3 is the most stable form.…”

“…[31][32][33][34][35] Likewise, pure vdW junction between metallic TMDs and β-Ga 2 O 3 seems unlikely in the present study. Figure 1b [36][37][38] Atomic force microscopy (AFM) to measure thickness of Nb(Ta)S 2 and β-Ga 2 O 3 has been conducted with MESFET structure, and exemplary 3D thickness profiles are thus shown in Figure 1c,d in literature (qΦ W of NbS 2 , [39,40] TaS 2 , [39,41] and β-Ga 2 O 3 [2,3] ≈6.0, ≈5.6, and ≈4.1 eV, respectively). Such difference is attributed to possible existence of ultrathin oxide (NbO x or TaO x ) on TaS 2 or NbS 2 , since those TMDs are so weak to oxidation in air ambient.…”

Solution‐Processable Epitaxial Metallic Delafossite Oxide Films

“…Delafossite structured ternary oxides and nitrides have always attracted great interests in fundamental sciences and technological applications during the past decades. [ 1–5 ] Specifically, metallic delafossite oxides (ABO 2 ), such as PdCrO 2 , PdCoO 2 , and PtCoO 2 showing extraordinarily high conductivity, have been adopted as a new benchmark for conductive oxides. [ 1 ] Delafossite ABO 2 has a natural superlattice‐like structure composed of alternatively stacked noble‐metal A‐atoms and edge‐sharing BO 6 oxygen octahedra with linear OAO ionic bonds to interlink the sublayers.…”

“…Recently, PdCoO 2 thin films have been successfully synthesized by molecular beam epitaxy (MBE) and pulsed laser deposition (PLD). [ 2,15–17 ] Specifically, Brahlek et al systematically investigated the growth of high‐quality epitaxial PdCoO 2 thin films (10 × 10 cm 2 ) by MBE, where the room temperature conductivity has reached as high as 2.6 × 10 5 S cm −1 for a 125 nm‐thick thin film annealed in oxygen. [ 17 ] It is suggested that metallic ABO 2 thin films can be potential utilized for various electronic devices ranging from low‐resistivity bottom electrodes for 2D materials to correlated transparent conductors.…”

“…[ 17 ] It is suggested that metallic ABO 2 thin films can be potential utilized for various electronic devices ranging from low‐resistivity bottom electrodes for 2D materials to correlated transparent conductors. [ 2,15–17 ] Moreover, as the isostructural compounds, PtCoO 2 has the lowest room temperature resistivity amongst the oxide system known, [ 1 ] and PdCrO 2 shows strong coupling between the antiferromagnetism and the conduction electrons. [ 18,19 ] Growing PtCoO 2 and PdCrO 2 thin films will expand the fundamental investigations and further potential applications of metallic delafossite oxides.…”