A new Al0.3Ga0.7As/GaAs modulation-doped FET

A new Al0.3Ga0.7As/GaAs modulation-doped FET fabricated like a MESFET but operating like a JFET was successfully fabricated and tested. This new device replaces the Schottky gate of the MESFET with an n+/p+ camel diode structure, thereby allowing problems associated with the former to be overcome. The devices, which were fabricated from structures grown by molecular beam epitaxy (MBE), had a 1µm gate length, a 290µm gate width, and a 4µm channel length. The room temperature transconductance normalized to the gate width was about 95 mS/mm, which is comparable to that obtained in similar modulation-doped Schottky barrier FET's. Unlike modulation-doped Schottky barrier FET's, fabrication of this new device does not require any critical etching steps or formation of a rectifying metal contact to the rapidly oxidizing Al0.3Ga0.7As. Relatively simple fabrication procedures combined with good device performance make this camel gate FET suitable for LSI applications.