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The gate orientation dependence of InGaAs/AlGaAs high electron mobility transistors (HEMTs) formed by the wet-chemical recess etching has been evaluated. The short channel effect strongly depends on the gate orientation and is significant in the order of [011], [001] and [011] oriented devices. Such orientation dependence results from a difference of the side-etching lengths, which are 0.01 µm, 0.03 µm and 0.06 µm for the [011], [001] and [011] oriented devices, respectively. The other characteristics of HEMTs such BV gd, gm and f T also depend on the gate orientation because of a difference of the recessed shape.

In the gate recess etching of O.1pm gate HEMT process, the anomalous phenomenon caused by electrochemical etching was found. The isolation region implanted with oxygen ion was etched more deeply than the channel region, which caused a non-flat etched surface. This anomaly effects seriously on the device performaince and its uniformity. We suppressed the anomaly by optimizing the condition of the isolation and the pattern of the device. Flat etched surface was achieved and uniform device characteristics was obtained.

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Schottky characteristics of InAlAs grown by metal-organic chemical vapor deposition (MOCVD) have been evaluated. InAlAs Schottky characteristics are strongly affected by MOCVD growth temperature. The reverse current of InAlAs grown at 700 • C is more than one order of magnitude larger than that at 750 • C. From deep-level transient spectroscopy (DLTS) measurements, electron traps with activation energies of 0.45, 0.33 and 0.15 eV have been observed in InAlAs grown at 700 • C.The results of C-V , Hall and secondary ion mass spectrometry (SIMS) measurements suggest that the trap is acceptor-type and seems to be related not to impurities but to intrinsic defects. The mechanism of the large reverse current in InAlAs grown at 700 • C is believed to be due to the conduction through the trap.