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A comparison is made between the electronic structures determined in ultrahigh vacuum of three surfaces using scanning tunneling spectroscopy ͑STS͒ and Kelvin probe force microscopy ͑KPFM͒. STS and KPFM illustrates Fermi level pinning of clean InAs͑001͒-͑4 ϫ 2͒ and InGaAs͑001͒-͑4 ϫ 2͒ surfaces and near flat band conditions for InAs͑110͒ cleaved surfaces. However, for InAs͑001͒-͑4 ϫ 2͒ and InGaAs͑001͒-͑4 ϫ 2͒, STS and KPFM data show very different positions for the surface Fermi level on identical samples; it is hypothesized that the difference is due to the Fermi level measured by KPFM being shifted by a static charge dipole to which STS is much less sensitive.

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Articles you may be interested inAtomic imaging of atomic layer deposition oxide nucleation with trimethylaluminum on As-rich InGaAs (001) 2 × 4 vs Ga/In-rich InGaAs(001) 4 × 2 J. Chem. Phys. 136, 154706 (2012); 10.1063/1.4704126Atomic imaging of the monolayer nucleation and unpinning of a compound semiconductor surface during atomic layer deposition Initiation of a passivated interface between hafnium oxide and In ( Ga ) As ( 0 0 1 ) − ( 4 × 2 )Pre-atomic layer deposition surface cleaning and chemical passivation of (100) In 0.2 Ga 0.8 As and deposition of ultrathin Al 2 O 3 gate insulators Using in situ atomic scale imaging with scanning tunneling microscopy/spectroscopy, a combination of atomic hydrogen dosing, annealing, and trimethyl aluminum dosing is observed to produce an ordered unpinned passivation layer on an air exposed InGaAs(001)-(4 Â 2) surface with only monatomic steps. This shows that conventional gate-last semiconductor processing can be employed to fabricate a variety of electronic devices, even on air exposed compound semiconductors.

Formation of a contaminant free, flat, electrically passive interface to a gate oxide such as a-Al(2)O(3) is the critical step in fabricating III-V metal oxide semiconductor field effect transistors; while the bulk oxide is amorphous, the interface may need to be ordered to prevent electrical defect formation. A two temperature in situ cleaning process is shown to produce a clean, flat group III or group V rich InGaAs surface. The dependence of initial surface reconstruction and dosing temperature of the seeding of aluminum with trimethylaluminum dosing is observed to produce an ordered unpinned passivation layer on InGaAs(001)-(4 × 2) surface at sample temperatures below 190 °C. Conversely, the InGaAs(001)-(2 × 4) surface is shown to generate an unpinned passivation layer with a seeding temperature up to 280 °C. For both reconstructions, the chemical drive force is consistent with formation of As-Al-As bonds. The optimal seed layer protects the surface from background contamination.