Oxidation of the GaAs semiconductor at the Al₂O₃/GaAs junction

Abstract

Atomic-scale understanding and processing of the oxidation of III-V compound-semiconductor surfaces are essential for developing materials for various devices (e.g., transistors, solar cells, and light emitting diodes). The oxidation-induced defect-rich phases at the interfaces of oxide/III-V junctions significantly affect the electrical performance of devices. In this study, a method to control the GaAs oxidation and interfacial defect density at the prototypical Al2O3/GaAs junction grown via atomic layer deposition (ALD) is demonstrated. Namely, pre-oxidation of GaAs(100) with an In-induced c(8 × 2) surface reconstruction, leading to a crystalline c(4 × 2)-O interface oxide before ALD of Al2O3, decreases band-gap defect density at the Al2O3/GaAs interface. Concomitantly, X-ray photoelectron spectroscopy (XPS) from these Al2O3/GaAs interfaces shows that the high oxidation state of Ga (Ga2O3 type) decreases, and the corresponding In2O3 type phase forms when employing the c(4 × 2)-O interface layer. Detailed synchrotron-radiation XPS of the counterpart c(4 × 2)-O oxide of InAs(100) has been utilized to elucidate the atomic structure of the useful c(4 × 2)-O interface layer and its oxidation process. The spectral analysis reveals that three different oxygen sites, five oxidation-induced group-III atomic sites with core-level shifts between -0.2 eV and +1.0 eV, and hardly any oxygen-induced changes at the As sites form during the oxidation. These results, discussed within the current atomic model of the c(4 × 2)-O interface, provide insight into the atomic structures of oxide/III-V interfaces and a way to control the semiconductor oxidation.

Oxidation of GaSb(100) and its control studied by scanning tunneling microscopy and spectroscopy

“…26 Thus, GaSb(100)(1 Â 3)-In-O is a hitherto unreported member for the crystalline oxidized III-V surfaces, 27 which have been shown to potentially decrease the defect densities at insulator/III-V interfaces. [28][29][30] The density of disorderinduced point defects can also be expected to decrease on GaSb(100)(1 Â 3)-In-O, but it is still unclear what kind of band structure is formed in the building block(s) of GaSb(100)(1 Â 3)-In-O itself, in relation to the GaSb band gap area. To clarify this, a comparison of the STS curves of GaSb(100)(4 Â 3) and (1 Â 3)-In-O is shown in Fig.…”

Decreasing Defect‐State Density of Al2O3/GaxIn1−xAs Device Interfaces with InOx Structures

“…Figure shows the PL spectra for each of the samples along with the LEED figures of the starting surface of GaAs(100)(6 × 6) and the observed intense (1 × 1)‐InO x as insets. For LEED patterns of the other surfaces, we refer to our previous works . The least amount of nonradiative recombination is observed for the c (4 × 2) sample, and the most for the (1 × 1) sample.…”

“…Indeed, the nature of these interface defects and the methods to control their formation have been the subject of a vast body of investigations (e.g., refs. ). In previous studies, these defect states have been found to arise, among others, from group‐V dimers; group‐V and group‐III dangling bonds; and III‐Ox or V‐Ox phases.…”

“…Thus, the identification of defect origin(s) is an open issue. There appears to be a consensus that the high oxidation state of Ga (i.e., Ga 2 O 3 type) increases defect density and is more harmful than the corresponding oxides of In . However, the mechanism responsible for Ga 2 O 3 ‐related gap states in Ga x In 1− x As remains unclear.…”

“…A potential approach, presented recently, includes the deposition of a thin In layer on GaAs, followed by the oxidation of such In‐terminated GaAs before the growth of an insulator film. This method leads to a crystalline oxidized In‐containing GaAs surface: GaAs(100) c (4 × 2)‐InO x , which is promising to be incorporated into device structures, because it is found to increase photoluminescence (PL) intensity of GaAs, ascribed to result from a reduction in defect state density …”