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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.

A systematic study of the electrical properties of Si-doped In0.52Al0.48As grown under various metalorganic vapor phase epitaxy (MOVPE) conditions such as V/III ratio and growth temperature is carried out. It is demonstrated that either high V/III ratios (≥64) or high growth temperatures (≥720°C) are necessary for obtaining good InAlAs electrical properties. For a small V/III ratio (=32) and low growth temperatures (≤700°C), a large discrepancy is found in Hall carrier concentration (n Hall), ionized impurity concentration (N C – V), and Si concentration (N Si); N C – V>N Si>n Hall; which can be explained by the dual formation of donor and acceptor deep levels. SIMS results suggest that carbon and oxygen impurities are not candidates for these deep levels, and other origins such as intrinsic defects, which are closely related to growth conditions, are applicable.

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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