A substrate processing apparatus includes: a tray provided in a vacuum processing container and having a recess that accommodates a target made of a low-melting-point material; a refrigerator that cools the tray; a substrate holder that holds a substrate; a reversal driver that reverses the position of the substrate holder upside down; and a rotation driver that rotates the substrate holder in a circumferential direction of the substrate.

High electron mobility transistors are provided which comprise a III-Nitride semiconductor layer comprising a III-Nitride semiconductor, in contact with a gallium oxide semiconductor layer comprising gallium oxide, forming an interface therebetween.

Embodiments according to the present invention provide a growth substrate wafer for high-performance GaN switching power devices, comprising: a Si growth substrate; a first AlN nucleation layer formed on the Si growth substrate; and a plurality of SiOx protrusions (Protrusion) discontinuously spaced apart and arranged on the first AlN nucleation layer, wherein the surface of the first AlN nucleation layer is exposed in the regions between the plurality of SiOx protrusions.

III-Nitrides epilayer(s) are grown remotely on a 2D material layer, such as graphene or h-BN, aBN, or polycrystalline BN coated crystalline substrate, where the Nitride-face surface of the epilayer faces the 2D material. A small mechanical force using a 2D material-based layer transfer process is used to separate the III-Nitrides epilayer(s) at their interface with the 2D material layer. Alternatively, the III-Nitrides epilayer is removed by mechanical force from a substrate with the assistance of a first thermal release tape and an optional metal layer on the epilayer and then a second thermal release tape and/or optional metal layer, is applied to the Nitride-face of the epilayer, the first thermal release tape and first metal layer are removed, the Ga-face surface is bonded to a substrate, and the second thermal release tape is removed. The resulting Nitride-face surface of the epilayer has high quality. A HEMT may be formed using the above structures.