Surface supersaturation during crystal growth can be obtained by measuring inter-step distance of spiral steps and with an equation given by Cabrera and Levine. Surface supersaturations thus measured for YBCO (YBa2Cu3O7), InP, SiC and GaN are presented. Surface supersaturation in the growth of YBCO depends strongly on growth temperature and decreases with the temperature irrespective of growth methods. Liquid phase epitaxy (LPE) of InP gives very low supersaturation which depends on the growth and saturation temperatures. Clear double spiral steps were found on vapor grown surface of SiC and it turned out that the surface supersaturation was considerably low as low as 0.02 for example. This is due to the high growth temperature. Experimentally obtained growth rate of GaN by metal organic vapor phase epitaxy (MOVPE) as a function of surface supersaturation showed a good agreement with BCF theory in low supersaturation limit as demonstrated by Akasaka et al..
