Absolute coverage measurements on sulphur-passivated GaAs(100)

Stoichiometry Study of S-Terminated GaAs(001)-(2 ×6) Surface with Synchrotron Radiation Photoelectron Spectroscopy

“…Moreover, the model with five S-S dimers is preferable from the viewpoint of local charge neutrality. Before the discovery of the (2 × 6) phase, several techniques were used to investigate the surface composition of the S-terminated GaAs(001) surface, including particleinduced X-ray emission, 8) synchrotron radiation photoelectron spectroscopy (SRPES) [9][10][11][12][13][14][15] and reflectance anisotropy (RA). 16) Moriaty et al 10) reported an SRPES study and suggested that As-As dimers coexisted with S-S dimers on an Sterminated GaAs(001) surface obtained from the GaAs(001) As-rich c(2 × 8) phase.…”

Understanding Thermal Evolution and Monolayer Doping of Sulfur-Passivated GaAs(100)

“…struction and the final state of the sulfur atoms remaining unresolved despite their importance in microelectronic interfaces and mass transport during MLD. Some studies have attributed the (2×1) phase to dimerization of surface S atoms, 27,33 while others have attributed its structural origin to the formation of either Ga− S 31 or As−S dimers, 32 which would imply desorption of half the S atoms. Clarification of the (2×1)-S reconstruction is therefore of great interest for understanding MLD performed without capping layers for its impact on resulting carrier densities, as well as for engineering heterostructures that incorporate Spassivated surfaces into nanoelectronic devices.…”

“…Collectively, these data indicate Ga−S bonding constitutes the dominant chemical state of S in the as-passivated surface, in agreement with previous reports of similarly prepared surfaces. 26,27 These data, along with the results from spectroscopic data discussed in subsequent sections, are summarized in Table 1.…”

“…Again, this observation points to a termination characterized by predominantly Ga−S bonding, consistent with previous spectroscopic studies of the (2 × 1)-S reconstruction. 26,27,35 Annealing to 813 K, however, results in a complete loss of the high-binding-energy shoulder of Ga 2p, which undergoes a substantial increase in its intensity. Similarly, the As 3d and Ga 3s levels intensities increase, while that of S 2p decreases dramatically, remaining just above the detection limit.…”

“…Having determined that the (2 × 1) reconstruction of S/ GaAs(100) is As-deplete relative to the bulk-terminated surface composition and characterized by the presence of Ga−S bonds, we can now consider structural models put forward in the As mentioned previously, the (1 × 1)-S surface (Figure 3A) is terminated by ∼1 monolayer of S atoms that bridge the secondlayer Ga atoms. In the model of the (2 × 1) surface proposed by Berkovits and Paget, 33 as well as by Xia et al 27 (shown in Figure 3B), the terminal S atoms dimerize, maintaining the same total number of surface S atoms as the (1 × 1) surface in Figure 3A. Together with the second-layer Ga atoms, these dimers form a ringlike structure above half of the third-layer As atoms, which would effectively produce a shadowing effect that prevents their detection in an LEIS measurement.…”