Oxidation of the GaAs semiconductor at the Al2O3/GaAs junction

Controlled high-quality interface of a Ti2.5O3(0 1 0)/GaAs(0 0 1) heterostructure enabled by minimized lattice mismatch and suppressed ion diffusion

Metal oxide/semiconductor heterostructures exhibit great potential for high-performance electronic device applications, but the interfacial defects resulting from lattice mismatch pose significant challenges to improving the performance of these devices. In this study, we reported a construction of a single crystal Ti_2.5O₃/GaAs heterostructure with minimum lattice mismatch between titanium sub-oxides and GaAs substrate. Low lattice mismatch values of 0.3% or 0.6% can be achieved along different orientations. Further experimental analyses demonstrate that high crystalline Ti_2.5O₃ (0 1 0) film can be grown layer by layer on GaAs (0 0 1) substrate with highly compatible interface. The defect-free interface significantly suppresses the diffusion of As and Ga ions, which impedes the formation of arsenic oxide and gallium oxide at the interface. Due to the high-quality Ti_2.5O₃ layer, the integrated BaTiO₃(250 nm)/SrTiO₃/Ti_2.5O₃(5 nm)/GaAs heterostructure exhibits an enhanced hysteresis loop with a remnant polarization of 9.85 µC/cm² at 600 kV/cm and a small leakage current density of 1 × 10^-5 A/cm² at -500 kV/cm. The considerable advantage of this Ti_2.5O₃/GaAs heterostructure provides an example of integrating other functional oxides for GaAs with suppressed ion diffusion. It also provides a platform for fabricating different electronic devices with higher reliability and performance.

Oxidation-Induced Changes in the ALD-Al2O3/InAs(100) Interface and Control of the Changes for Device Processing

InAs crystals are emerging materials for various devices like radio frequency transistors and infrared sensors. Control of oxidation-induced changes is essential for decreasing amounts of the harmful InAs surface (or interface) defects because it is hard to avoid the energetically favored oxidation of InAs surface parts in device processing. We have characterized atomic-layer-deposition (ALD) grown Al₂O₃/InAs interfaces, preoxidized differently, with synchrotron hard X-ray photoelectron spectroscopy (HAXPES), low-energy electron diffraction, scanning tunneling microscopy, and time-of-flight elastic recoil detection analysis. The chemical environment and core-level shifts are clarified for well-embedded InAs interfaces (12 nm Al₂O₃) to avoid, in particular, effects of a significant potential change at the vacuum-solid interface. High-resolution As 3d spectra reveal that the Al₂O₃/InAs interface, which was sputter-cleaned before ALD, includes +1.0 eV shift, whereas As 3d of the preoxidized (3 × 1)-O interface exhibits a shift of -0.51 eV. The measurements also indicate that an As₂O₃ type structure is not crucial in controlling defect densities. Regarding In 4d measurements, the sputtered InAs interface includes only a +0.29 eV shift, while the In 4d shift around -0.3 eV is found to be inherent for the crystalline oxidized interfaces. Thus, the negative shifts, which have been usually associated with dangling bonds, are not necessarily an indication of such point defects as previously expected. In contrast, the negative shifts can arise from bonding with O atoms. Therefore, specific care should be directed in determining the bulk-component positions in photoelectron studies. Finally, we present an approach to transfer the InAs oxidation results to a device process of high electron mobility transistors (HEMT) using an As-rich III-V surface and In deposition. The approach is found to decrease a gate leakage current of HEMT without losing the gate controllability.

Adsorption and dynamics of group IV, V atoms and molecular oxygen on semiconductor group IV (0 0 1) surfaces

In this review we address (1) the co-adsorption of group V (As, Sb, Bi) atoms and molecular oxygen on the Si(0 0 1) surface and (2) the adsorption and dynamics of Sb, Bi, Si and Ge ad-dimers on the Si(0 0 1) and Ge(0 0 1) surfaces. The adsorption and diffusion processes of group IV and V atoms on the (0 0 1) surfaces of group IV semiconductor surfaces have been studied using multi-configuration self-consistent field methods and density functional theory calculations. Results obtained by various types of first-principle total energy calculations are mutually compared and discussed. Our results demonstrate the capability of these quantum chemistry methods to provide relevant and reliable information on the interaction between adsorbate and semiconductor surfaces.