Functional characteristics, comprising enhance-mode linear amplification performance and N-shaped negative-differential resistance phenomenon, have been observed in an inverted δ-doped In0.34Al0.66As0.85Sb0.15∕In0.75Ga0.25As∕InP high electron mobility transistor with the asymmetric source/drain terminal structure. Unpassivated peak performances, including the transconductance of 268mS∕mm and saturation drain current density of 210mA∕mm, and significant negative differential resistance characteristics, including the peak-to-valley current ratio of 6.1, can be obtained on the same device by switching the source/drain electrical connection. The electric field aspects of the asymmetry in the contacts have also been investigated. At the request of the authors, this article is being retracted effective 19 August 2005.