Contacting materials and methods for forming ohmic contact to the N-face polarity surfaces of Group-III nitride based semiconductor materials, and devices fabricated using the methods. A logic gate array comprises a plurality of vertical ultrathin transistors coupled together. The system compiles this source program into an intermediate representation. Multiple well heads can be prepared for within a given cellar, simultaneously. The PCV gas and the part of the intake air are forced to flow into the driving gas side of the air ejector, so that the air ejector functions as a vacuum pump.