Structural, optical, and electrical properties of orthorhombic κ-(InxGa1−x)2O3 thin films

Abstract

Material properties of orthorhombic κ-phase (InxGa1−x)2O3 thin films grown on a c-plane sapphire substrate by pulsed-laser deposition are reported for an indium content up to x ∼ 0.35. This extended range of miscibility enables band gap engineering between 4.3 and 4.9 eV. The c-lattice constant as well as the bandgap depends linearly on the In content. For x > 0.35, a phase change to the hexagonal InGaO3(ii) and the cubic bixbyite structure occurred. The dielectric function and the refractive index were determined by spectroscopic ellipsometry as a function of the alloy composition. We propose zirconium to induce n-type conductivity and have achieved electrically conducting thin films with a room temperature conductivity of up to 0.1 S/cm for samples with a low In content of about x = 0.01. Temperature-dependent Hall-effect measurements yielded a thermal activation energy of the free electron density of 190 meV. Schottky barrier diodes with rectification ratios up to 106 were investigated by quasi-static capacitance voltage and temperature-dependent current voltage measurements.

Band Offsets at κ-([Al,In]xGa1–x)2O3/MgO Interfaces

“…Subniveau transition energies in the conduction band of QWs can therefore be tuned up to a value of 1.1 eV such that detectable wavelengths from the far IR up to the visible might be covered by QWIPs in the investigated composition range. Figure 5: Summary of the energy levels at the a) (InxGa1-x)2O3/MgO interface and b) at the (AlxGa1-x)2O3/MgO interface as determined from XPS (red) and transmission 23,24 (blue) measurements. The measured energy levels render the (AlxGa1-x)2O3/(InxGa1-x)2O3/(AlxGa1x)2O3 a promising heterostructure for quantum wells.…”

“…The exact target geometries can be found in References 24,25,45 . The presence of tin is necessary to facilitate the growth of the Ga2O3 based layers in the metastable orthorhombic modification for the PLD deposition method [18][19][20]23 . However, no significant amount of tin is incorporated during growth, such that this species only serves as surfactant or catalyst to stabilize the κ-phase and not as a dopant.…”

“…Recently, one report even achieved conductive doping of this phase by Si or Sn incorporation, which is necessary for a variety of device applications 36 . However, in PLD and MBE growth, tin is necessary as catalyst to stabilize the orthorhombic modification at all, but is not incorporated in the thin film layer as active donor element [18][19][20][23][24][25]44 . Further, several reports already deal with the alloying of this phase with indium 23,25,38 or aluminum 24,40 in a broad composition range, including bandgap engineering and the evolution of lattice constants.…”

Structural and Elastic Properties of α‐(AlxGa1−x)2O3 Thin Films on (11.0) Al2O3 Substrates for the Entire Composition Range

“…[ 6 ] The second‐most stable structure is the orthorhombic κ ‐phase, for which ternary PLD thin films were already reported. [ 7–11 ] The third‐most stable polymorph is the rhombohedral α‐phase.…”

Epitaxial Growth of κ‐(AlxGa1−x)2O3 Layers and Superlattice Heterostructures up to x = 0.48 on Highly Conductive Al‐Doped ZnO Thin‐Film Templates by Pulsed Laser Deposition

“… can be grown heteroepitaxially by several deposition methods, such as pulsed‐laser deposition [ 14,19–26 ] (PLD), halide vapor phase epitaxy [ 18,27–29 ] (HVPE), metal‐organic chemical vapor deposition [ 17,30–35 ] (MOCVD), metal‐organic vapor phase epitaxy [ 36–39 ] (MOVPE), atomic layer deposition, [ 31 ] molecular beam epitaxy [ 40 ] (MBE), plasma‐assisted molecular beam epitaxy [ 41 ] (PAMBE), and mist CVD. [ 15,16,42–49 ]…”