We examined a negative differential resistance (NDR) in 2D electron gas (2-DEG) of the 0.1 mu m psuedomorphic high electron mobility transistors (HEMTs) by adopting two types of the gate structures. A single gate structure exhibits a clear 2-DEG NDR effect at a drain voltage of similar to 3.7 V and produces a similar to 10 times greater electric field (similar to 30 kV/cm) for the NDR than that of the bulk InGaAs semiconductors. The triple gate structure suppresses the NDR effect at the same bias condition but gives rise to the NDR recovery at a positive drain-control gate bias while significantly decreasing the break down voltage. (C) 2004 The Electrochemical Society.