An x-ray photoelectron spectroscopy study on ozone treated GaAs surfaces

Abstract

The formation of sacrificial oxides on GaAs is a well established procedure in the preparation of in situ cleaned substrates for epitaxial growth. Oxides formed from ozone exposure promise a more controlled alternative to thermal and air formed oxides. This paper reports on a study of the composition and structures of oxides on GaAs(100) surfaces and, in addition, examines the persistence of carbon-containing species at the oxide surface and oxide–semiconductor interface. X-ray photoelectron spectroscopy (XPS) was used in a high spectral resolution mode, to distinguish between the different oxide phases formed. Surfaces oxidized under ozone for 10–30 min had Ga/As oxide ratios close to unity. By contrast, acid treated, DI water rinsed surfaces exposed to air produce oxides rich in either Ga or As depending on conditions. Heating of the ozone-produced oxide to ≥600 °C results in sequential decomposition of As2O5, As2O3, and Ga2O3. Oxide layers produced by short-term ozone exposures were analyzed by angle-resolved XPS. A 10 min exposure produced an oxide of 2.0 nm thickness. Surface carbon-containing contaminants were removed to a level ≤0.2 monolayer by heating the specimen to 400 °C in vacuum (base pressures of 2×10−8 Pa). Surfaces heated to ≥600 °C to desorb all oxides, also showed no evidence of carbon-containing species and the As/Ga ratio was unity.

The formation of supported monodisperse Au nanoparticles by UV/ozone oxidation process

“…Holloway and Mueller [19] have already pointed out the importance of oxides, formed after such chemical etchings as treatments A and B, that enhance the Au/ GaAs reaction to more readily form pits. The composition of these air-and water-produced native oxides strongly depends on the experimental conditions [20] and was not determined within the framework of the current study.…”

In situ study of surface reactions of atomic layer deposited LaxAl2−xO3 films on atomically clean In0.2Ga0.8As

“…27,28 The chemical shift found here is substantially lower than in Ga 2 O 3 suggesting the formation of a Ga-suboxide most likely in the following bond environment: substrate-Ga-O-Al ͑or La͒. 28 Similarly, the As 2p 3/2 shows an additional component at 0.63 eV above the position of the As-bulk peak ͑1322.4 eV͒ and is associated with As-As bonding. 27 The area ratio of the nonbulk/bulk Ga and As components are 0.31 and 0.49, respectively.…”

Smoothness and cleanliness of the GaAs (100) surface after thermal desorption of the native oxide for the synthesis of high mobility structures using molecular beam epitaxy

“…Whilst it is widely accepted that a smooth substrate is desirable for the growth of high mobility 2DEG structures, to our knowledge no quantitative study has been conducted on the trade-off between minimal surface roughening and the complete removal of the amorphous native oxide. Studies of GaAs oxide desorption in vacuum have shown that the native surface oxide comes off in two steps [1]: the arsenic oxide evaporates first in the 4002500 1C range [2,3], followed by the gallium oxide at temperatures $ 600 1C [4][5][6][7][8]. This process can damage the wafer as the oxide removal is non-uniform, resulting in masking by residual oxide areas versus regions of clean GaAs [9].…”