The present disclosure describes epitaxial oxide high electron mobility transistors (HEMTs). In some embodiments, a HEMT comprises: a substrate; a template layer on the substrate; a first epitaxial semiconductor layer on the template layer; and a second epitaxial semiconductor layer on the first epitaxial semiconductor layer. The template layer can comprise crystalline metallic Al(111). The first epitaxial semiconductor layer can comprise (Al.sub.xGa.sub.1-x).sub.yO.sub.z, wherein 0≤x≤1, 1≤y≤3, and 2≤z≤4, wherein the (Al.sub.xGa.sub.1-x).sub.yO.sub.z comprises a Pna21 space group, and wherein the (Al.sub.xGa.sub.1-x).sub.yO.sub.z comprises a first conductivity type formed via polarization. The second epitaxial semiconductor layer can comprise a second oxide material.

A vertical field effect transistor according to an embodiment of the present invention does not require a spacer and, accordingly, remarkably alleviates the problem that electric charge is scattered at an interface, thereby having excellent electrical characteristics. The vertical field effect transistor includes a substrate, a source electrode positioned on the substrate, an active layer positioned on the source electrode and having vertically grown crystal grains, a drain electrode positioned on the active layer to be spaced by the active layer away from the source electrode, a gate insulating layer positioned on a lateral surface of the active layer, and a gate electrode positioned on the gate insulating layer.

A method for manufacturing a semiconductor film includes placing a semiconductor substrate including a β-Ga.sub.2O.sub.3-based single crystal in a reaction chamber of an HVPE apparatus. When the semiconductor substrate is placed so that the growth base surface faces upward, an inlet for a dopant-including gas into the space is positioned higher than an inlet for an oxygen-including gas into the space and an inlet for a Ga chloride gas into the space is positioned higher than the inlet for the dopant-including gas into the space. When the semiconductor substrate is placed so that the growth base surface faces downward, the inlet for the dopant-including gas into the space is positioned higher than the inlet for the Ga chloride gas into the space and the inlet for the oxygen-including gas into the space is positioned higher than the inlet for the dopant-including gas into the space.

The present disclosure describes epitaxial oxide high electron mobility transistors (HEMTs). In some embodiments, a HEMT comprises: a substrate; a first epitaxial semiconductor layer on the substrate; and a second epitaxial semiconductor layer on the first epitaxial semiconductor layer. The first epitaxial semiconductor layer can comprise a first oxide material, wherein the first oxide material can comprise a first polar material with an orthorhombic, tetragonal or trigonal crystal symmetry, and wherein the first oxide material can comprise a first conductivity type formed via polarization. The second epitaxial semiconductor layer can comprise a second oxide material.

A semiconductor film, a sheet like object, and a semiconductor device are provided that have inhibited semiconductor properties, particularly leakage current, and excellent withstand voltage and heat dissipation. A crystalline semiconductor film or a sheet like object includes a corundum structured oxide semiconductor as a major component, wherein the film has a film thickness of 1 μm or more. Particularly, the semiconductor film or the object includes a semiconductor component of oxide of one or more selected from gallium, indium, and aluminum as a major component. A semiconductor device has a semiconductor structure including the semiconductor film or the object.

A method of growing a conductive Ga.sub.2O.sub.3-based crystal film by MBE includes producing a Ga vapor and a Si-containing vapor and supplying the vapors as molecular beams onto a surface of a Ga.sub.2O.sub.3-based crystal substrate so as to grow the Ga.sub.2O.sub.3-based crystal film. The Ga.sub.2O.sub.3-based crystal film includes a Si-containing Ga.sub.2O.sub.3-based single crystal film. The Si-containing vapor is produced by heating Si or a Si compound and Ga while allowing the Si or a Si compound to contact with the Ga.

Methods and systems for forming complex oxide films are provided. Also provided are complex oxide films and heterostructures made using the methods and electronic devices incorporating the complex oxide films and heterostructures. In the methods pulsed laser deposition is conducted in an atmosphere containing a metal-organic precursor to form highly stoichiometric complex oxides.

The disclosure provides a semiconductor apparatus capable of keeping a semiconductor characteristics and realizing excellent semiconductor properties even when using an n type semiconductor (gallium oxide, for example) having a low loss at a high voltage and having much higher dielectric breakdown electric field strength than SiC. A semiconductor apparatus includes a gate electrode and a channel layer formed of a channel directly or through other layers on a side wall of the gate electrode, and wherein a portion of or whole the channel layer may be a p type oxide semiconductor (iridium oxide, for example).

A semiconductor device includes a semiconductor layer including a Ga.sub.2O.sub.3-based single crystal, and an electrode that is in contact with a surface of the semiconductor layer. The semiconductor layer is in Schottky-contact with the electrode and has an electron carrier concentration based on reverse withstand voltage and electric field-breakdown strength of the Ga.sub.2O.sub.3-based single crystal.

A laminate including: a crystal substrate; and a semiconductor film provided on a main surface of the crystal substrate, the semiconductor film being mainly made of an oxide semiconductor containing a dopant and having a corundum structure, where the oxide semiconductor has a silicon concentration of 5.0×10.sup.20 cm.sup.−3 or less, and the semiconductor film has a resistivity of 150 mΩ.Math.cm or less. This provides a laminate including a semiconductor having low resistance and a corundum structure suitable for use in semiconductor devices.