Method and apparatus for growing indium oxide (In2O3) single crystals and indium oxide (In2O3) single crystal

A method for growing bulk In2O3 single crystals, comprising the steps of:

• i) providing into a growth chamber a thermal system comprising a noble metal crucible containing an initially non-conducting In2O3 starting material, a crucible thermal insulation surrounding the noble metal crucible at a bottom and a side, and an induction coil disposed around the noble metal crucible and coupled to a radio frequency generator, wherein a crucible wall thickness (th) is not greater than a penetration depth of an eddy current induced in the noble metal crucible wall by the induction coil:
• th≤δ=√{square root over (1/(πfμσ))}
• where δ is the penetration depth (or a skin depth), f is a generator frequency, μ is a permeability, and σ is an electrical conductivity of the noble metal crucible, the generator frequency being in a range between 1 kHz and 2 MHz;
• ii) closing the noble metal crucible with a cover of the thermal system comprising at least a lid and having at least one evacuation passage for removing gaseous decomposition products of In2O3 from an interior of the noble metal crucible and keeping the interior of the noble metal crucible in communication with a growth atmosphere, wherein a cross-section area of the at least one evacuation passage is 30% or less of a cross-section area of the crucible;
• iii) introducing at least into the thermal system the growth atmosphere, which provides oxygen partial pressure between 0.005 bar and 0.2 bar around a melting point of In2O3;
• iv) heating the In2O3 starting material by conduction and radiation from the noble metal crucible which in turn is inductively heated by the induction coil;
• v) keeping at least inside the thermal system an oxygen partial pressure which is insufficient to avoid In2O3 decomposition, thus decomposing in a controlled way the In2O3 starting material during heating of the noble metal crucible, thereby increasing electrical conductivity of the In2O3 starting material with rising temperature;
• vi) inducing, through the wall of the noble metal crucible, an eddy current in the In2O3 starting material, which becomes conducting around its melting point;
• vii) melting the In2O3 starting material to form a melt comprising liquid In2O3 starting material by a combination of conductive, radiative, and electrical heating, the electrical heating being caused by the eddy current induced directly in the In2O3 starting material;
• viii) electromagnetically levitating at least a portion of the liquid In2O3 starting material and forming at the same time a neck portion of the liquid In2O3 extending from the levitating top portion of the melt towards a bottom portion of the liquid In2O3 starting material at the crucible bottom, or towards the crucible bottom if all the liquid In2O3 starting material is levitating;
• ix) monitoring and detecting the melting point of the In2O3 starting material by at least one melting detection means;
• x) cooling the noble metal crucible containing the liquid In2O3 starting material to room temperature;
• and,
• xi) solidifying during cooling down the liquid In2O3 starting material and forming at the same time at least one bulk In2O3 single crystal from the levitating and non-levitating portions of the liquid In2O3 starting material, which solidifies on top and bottom sides of the liquid neck portion acting as a seed, or on a top side of the liquid neck portion if all liquid In2O3 starting material is levitating.