Double-clamped InAs/AlGaSb nanobeams 50 nm thick and 50-200 nm wide were fabricated using electron beam lithography, and their piezoresistance was measured and analyzed. Deep etching of a sacrificial layer produced an arched beam due to the shear stress arising from lattice mismatch, while shallow etching yielded a straight beam. The measured gauge factor and piezoresistance coefficient were positive or negative depending on whether the beam was straight or arched, respectively, and were much larger in magnitude than those for bulk InAs. These surprising phenomena are roughly explainable in terms of the piezoelectric effect in the thin films of the heterostructure. An analysis of the calculated piezoelectricity (PE) and piezoresistance yielded guidelines for obtaining a higher piezoresistance, and thus a higher sensitivity, in nanomechanical sensors made using such a heterostructure. (c) 2006 Elsevier B.V. All rights reserved.