Quantized conductance is observed in an InAs/AlSb ballistic constriction with channel length of 1.0 μm, at 4.2 K. In this structure eight conductance steps are detected, all within 20% of their theoretical values for purely ballistic transport. Compared to a shorter constriction (L=0.20 μm) located on the same mesa, relatively little degradation of the quantization is observed for the longer device. Possible reasons for the enhanced length performance of InAs/AlSb constrictions compared to similar structures fabricated in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterostructures are discussed.

• Received 17 January 1994

DOI:https://doi.org/10.1103/PhysRevB.49.8514