We investigate α-(AlxGa1-x)2O3 layers deposited by PLD for 0≤x≤1 on a- and m-plane sapphire. RSM measurements reveal a fundamental difference for these planes. Pseudomorphic α-(AlxGa1-x)2O3 on m-plane sapphire shows a shear strain e'5 along the c-axis vanishing on a-plane sapphire. Similarly, only relaxed m-plane α-(AlxGa1-x)2O3 exhibits a global lattice tilt in c-axis direction. Modeling of lattice constants and e'5 as function of x prove the shear strain to be due to the non-vanishing C14 component of the stress-strain tensor for α-(AlxGa1-x)2O3 contributing only for the m-plane. We further explain the occurrence of the lattice tilt and identify possible relaxation mechanisms.
We present κ-Ga2O3 layers grown by tin-assisted PLD on highly conductive Al-doped ZnO back contact layers. κ-Ga2O3 deposited on c-sapphire typically exhibits no lateral current flow. Significant currents can only be detected when a vertical current flow through the κ-Ga2O3 layer is enabled by the back contact confirming a strong conductivity anisotropy possibly due to suppressed transport across rotational domain boundaries. Pt/PtOx or Pd/PdOx Schottky contacts and NiO or ZnCo2O4 p-type contacts exhibit rectification ratios up to seven orders of magnitude. Further, we obtain a mean barrier height of ~2.1 eV and ideality factors as low as ~1.3 for Pt/PtOx/κ-Ga2O3 Schottky barrier diodes.
We have fabricated a novel type of ultracompact spectrometer without dispersive element(s) suitable for the use in smartphones. It comprises a waveguide with a linear photodetector array on top. The photosensitive layer features a steep chemical concentration gradient, fabricated from (MgxZn1-x)O, allowing for spectral detection in the UV. The dimensions of the device make it ultracompact with a volume of less than 1 cubic millimeter.
Recently, immense interest in the semiconductor Ga₂O₃ arose due to its large bandgap and high predicted electrical breakdown field. By alloying Ga₂O₃ with In₂O₃ or Al₂O₃, its bandgap can be tuned over a large range, allowing possible applications in heterostructure devices or devices with an adjusted absorption energy. For this purpose, property screening over a large composition range is crucial.
In this contribution, we present electrical, optical and structural properties of (Ga,In)₂O₃ and (Ga,Al)₂O₃ thin films grown by continuous composition spread pulsed laser deposition. The influence of growth parameters on phase boundaries were investigated and unipolar devices were fabricated.
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