Temperature programed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) were carried out on oxidized GaAs (001) surfaces in order to obtain insight into the durability of the oxide masks used in in situ selective-area processing. The TPD spectra comprised three successive desorption peaks showing the desorption of arsenic at 390°C, Ga2O at 475°C, and both Ga2O and arsenic above 500°C. XPS revealed the disappearance of As oxide and an increase of Ga oxide during the first desorption. The coexistence of two forms of Ga oxide, i.e., Ga2O and Ga2O3, is suggested, and a mechanism of oxide desorption is proposed.
A real-time mass spectroscopic observation of liberated species was carried out to investigate the mechanism of atomic-hydrogen-( H•)-induced deoxidation of GaAs native oxides. Atomic hydrogen treatment at 410°C caused, initially, the liberation of molecular arsenic ( As2/As4), resulting in the removal of As oxides, which was then followed by the liberation of Ga2O, leading to complete deoxidation. These results indicate that the deoxidation proceeds through two stages. The main chemical reactions are As2O
x
+2 x H•→ x H2O+ As2/(1/2As4) in the first stage and Ga2O3+ 4H•→2H2O+ Ga2O in the second stage.
Atomic hydrogen (H·)-induced modification of Ga2O3-like oxide on GaAs (001) was studied by temperature-programmed desorption. H· treatment at 300°C caused a new Ga2O desorption starting at around 400°C, whereas a sample treated with molecular hydrogen gave simultaneous desorption of Ga2O and elemental As only above 500°C, the same as observed in the untreated sample. X-ray photoelectron spectroscopy showed a reduction in O1s intensity after the H· treatment. These results indicate that atomic hydrogen converts Ga2O3-like oxide into volatile Ga2O-like oxide and consequently lowers the oxide-removal temperature.
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