Hydrogen can decrease the Schottky barrier height (SBH) of Ti/n diodes as much as 0.18 eV. Zero bias annealing (ZBA) makes the SBHs of Ti/n-GaAs diodes containing hydrogen decrease and reverse bias annealing (RBA) makes them increase. When RBA at 100-degrees-C lasts for 2 h or more, the SBHs haw a one-to-one correlation with the biases of RBA and the larger the bias applied, the higher the SBH is.