Abstract: Actuator controller comprising a body (12) with an inlet port (14) coupled to a source of pressurized fluid and in flow communication with primary and secondary spool bores (16, 20); primary and secondary spools (60, 62); first and second cross flow ports (48, 52) communicating said primary and secondary spool bores, compression and expansion outlet ports (53, 54) for applying pressurized fluid to a return-biased actuator (110); and a venting outlet port (23); wherein return action of the working piston of the actuator is facilitated with aid of pressurized fluid already gained in the system.

Abstract: A method for growing bulk GaN and AlGaN single crystal boules, preferably using a modified HVPE process, is provided. The single crystal boules typically have a volume in excess of 4 cubic centimeters with a minimum dimension of approximately 1 centimeter. If desired, the bulk material can be doped during growth to achieve n-, i-, or p-type conductivity. In order to have growth cycles of sufficient duration, preferably an extended Ga source is used in which a portion of the Ga source is maintained at a relatively high temperature while most of the Ga source is maintained at a temperature close to, and just above, the melting temperature of Ga. To grow large boules of AlGaN, preferably multiple Al sources are used, the Al sources being sequentially activated to avoid Al source depletion and excessive degradation.