In his recent paper ‘‘Rectification in heavily dopedp‐type GaAs/AlAs heterojunctions’’ [J. Appl. Phys.70, 1081 (1991)] Yoffe presented calculations of barrier heights and current‐voltage characteristics. Unfortunately, he adopted a typographical error in his basic equations. In this comment we show that significant differences in barrier heights and currents across heterojunctions arise, using the corrected expression for the calculations.