Investigation of neutralized (NH4)2S solution passivation of GaAs (100) surfaces

Synchrotron radiation photoelectron spectroscopy combined with scanning electron microscopy (SEM) and gravimetry has been used to study GaAs (100) surfaces treated with a neutralized (NH4)2S solution. Compared to the conventional basic (NH4)2S solution treatment, a thick Ga sulfide layer and strong Ga–S bond were formed on the GaAs surface after dipping GaAs wafers in a neutralized (NH4)2S solution. Gravimetric data show that the etching rate of GaAs in the neutralized (NH4)2S solution is about 15% slower than that in the conventional (NH4)2S solution. From SEM observation, fewer etching pits with smaller sizes were found on the neutralized (NH4)2S-treated GaAs surface.