DIRECT WRITING OF ACTIVE LOADS BY FOCUSED ION-BEAMS

With a 100 nm focus of a focused Ga+ ion beam with 100 keV, we write i nsulating lines in electronic layers of In0.21Ga0.79As quantum wells. In this way, in-plane-gate (IPG) transistors are formed which can be o perated at room temperature. In a typical integration application of a common source circuit, the pull-up resistance represents a serious pr oblem due to the high geometric aspect ratio necessary for it. For exa mple, the typical specific sheet resistivity of the In0.19Ga0.79As qua ntum well of 1.2 k Omega needs to be increased to 100 k Omega by a 1 m u m wide, about 83 mu m long channel. In order to save this waste of a rea we introduce active loads in the form of a narrow channel. In this way, the pull-up resistor requires orders of magnitude less area and stabilizes the drain current due to velocity saturation, leading to lo wer supply voltages. Inverters in this technology are presented and ch aracterized. In finite element simulations these circuits are further investigated. The operation of these systems is based on the lateral d epletion of adjacent quantum well areas. The basic differences between depletion within pn half spaces and pn half planes are discussed anal ytically, showing a marked dependence on dimensionality. In particular , it is shown that the ruggedness of IPGs can be explained by these ph enomena. (C) 1998 American Vacuum Society.