An enhancement-mode In0.52Al0.48As/In0.6Ga0.4As tunneling real-space transfer high electron mobility transistor (HEMT) was fabricated. The studied device operates as a conventional enhancement-mode HEMT under a low gate electrode bias. As the gate electrode bias increases, the electric field applied between the gate electrode and the InGaAs channel increases and the electrons in the channel become "hot." If the transverse field is sufficiently large, then the electrons in the InGaAs channel layer may have enough energy to overcome the barrier and tunnel into the gate electrode, thus I-DS decreases as I-G increases. Therefore, pronounced N-shaped negative differential resistance phenomenon and negative transconductance are observed in the studied device. (C) 2004 American Vacuum Society.