Sb-based pN heterojunction diodes at 6.2 angstrom, consisting of narrow bandgap p-type In(0.27)Ga(0.73)Sb and wide bandgap n-type In(0.69)Al(0.41)As(0.41)Sb(0.59), have been fabricated and measured. These diodes show excellent electrical characteristics with an ideality factor of 1.2 and high current density. S-parameter measurements and subsequent analysis show that these diodes have RC-cutoff frequencies over 1 THz, making these diodes excellent choices for high-frequency applications, such as sub-harmonic mixers for frequency conversion. Published by Elsevier Ltd.