InAs-based heterostructure barrier varactor (HBV) diodes with In0.3Al0.7As0.4Sb0.6 as the barrier material are demonstrated. Current-voltage and capacitance-voltage characteristics, as well as S-parameters, of HBV diodes with varying barrier thicknesses are examined. Maximum capacitance values and maximum-to-minimum capacitance ratios greater than those predicted by traditional HBV models were measured. The HBVs' unconventional behavior in terms of charge accumulation layers adjacent to the wide bandgap barrier is discussed. Published by Elsevier Ltd.