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

Area of Science:

• Materials Science
• Surface Science
• Semiconductor Device Physics

Background:

• Indium Arsenide (InAs) crystals are crucial for radio frequency transistors and infrared sensors.
• Controlling oxidation-induced surface and interface defects in InAs is essential for device performance.
• Energetically favored oxidation of InAs surfaces complicates device processing.

Purpose of the Study:

• To characterize atomic-layer-deposition (ALD) grown Al2O3/InAs interfaces with varying pre-oxidation states.
• To clarify the chemical environment and core-level shifts at the Al2O3/InAs interface.
• To investigate the origin of negative photoelectron shifts and their relation to defects.

Main Methods:

• Synchrotron hard X-ray photoelectron spectroscopy (HAXPES) was employed for chemical analysis.
• Low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and time-of-flight elastic recoil detection analysis (ToF-ERDA) were utilized.
• Characterization focused on well-embedded InAs interfaces (12 nm Al2O3) to mitigate potential changes.

Main Results:

• Sputter-cleaned Al2O3/InAs interfaces showed a +1.0 eV As 3d shift, while preoxidized interfaces exhibited a -0.51 eV shift.
• In 4d shifts were +0.29 eV for sputtered interfaces and -0.3 eV for crystalline oxidized interfaces.
• Negative shifts were attributed to oxygen bonding rather than dangling bonds or point defects.

Conclusions:

• The study clarifies the chemical nature of Al2O3/InAs interfaces, distinguishing between sputter-induced and oxidation-induced effects.
• An approach using an As-rich III-V surface and In deposition for high electron mobility transistors (HEMTs) was developed.
• This approach successfully reduced HEMT gate leakage current without compromising gate controllability.