Preparation of clean InP(100) surfaces studied by synchrotron radiation photoemission

Abstract

Wet chemical cleaning of InP surfaces investigated by in situ and ex situ infrared spectroscopyDependence of indium-tin-oxide work function on surface cleaning method as studied by ultraviolet and x-ray photoemission spectroscopiesThe chemical cleaning of indium phosphide ͑InP͒,͑100͒ surfaces is studied systematically by using photoemission electron spectroscopy. In order to achieve the necessary surface sensitivity and spectral resolution, synchrotron radiation with photon energies ranging from 60 to 600 eV are used to study the indium 4d, phosphorus 2p, carbon 1s, and oxygen 1s core levels, and the valence band. Typical H 2 SO 4 :H 2 O 2 :H 2 O solutions used to etch GaAs͑100͒ surfaces are applied to InP͑100͒ surfaces. It is found that the resulting surface species are significantly different from those found on GaAs͑100͒ surfaces and that a second chemical cleaning step using a strong acid is required to remove residual surface oxide. This two-step cleaning process leaves the surface oxide free and with approximately 0.4 ML of elemental phosphorus, which is removed by vacuum annealing. The carbon coverage is also reduced dramatically from approximately 1 to about 0.05 ML. The chemical reactions are investigated, the resulting InP surface species at different cleaning stages are determined, and the optimum cleaning procedure is presented.

Optimized cleaning method for producing device quality InP(100) surfaces

“…The one on the left with kinetic energy 1.35 ± 0.05eV lower than bulk peak (i.e. higher binding energy) is assigned as elemental Phosphorous in our early study [14], with coverage of about 0. At the beginning of the reaction, H atoms bind to the surface phosphorous atoms, so the surface will have a hydrogen termination on the phosphorous sites after treatment with a strong acid solution.…”

In situ study of the role of substrate temperature during atomic layer deposition of HfO2 on InP

“…For the S-passivated sample, the In-S/O concentration is very small and does not change significantly after ALD at different temperatures. Figure 2 shows the P 2p spectra from the (a) native oxide, (b) acid etched, (c) S-passivated samples, before ALD, and after 10 cycles of HfO 2 ALD at 200 C, 250 C and 300 C. The peak with a binding energy separation of þ4.0 eV to the InP bulk peak is assigned to P-OH bonding; 24 the peak with a binding energy separation of þ4.5 eV to the InP bulk peak is assigned to InPO 4 , and the peak with a binding energy separation of þ5.1 eV is assigned to In(PO 3 ) 3 . 19,23 Figure 2(d) shows the ratio of the total P-oxide peak area to that of the InP bulk peak of each respective surface.…”

Surface and Interfacial Reaction Study of Half Cycle Atomic Layer Deposited Al$_{2}$O$_{3}$ on Chemically Treated InP Surfaces

“…This study looks at the ''half cycle'' interaction between atomic-layer deposited (ALD) aluminum oxide (Al 2 O 3 ) film growth on (NH 4 ) 2 S treated and acid etched InP surfaces to determine the resultant interfacial chemistry between the trimethyl aluminum (TMA) ALD precursor and the substrate to investigate whether the reported oxide ''clean up'' effect seen on GaAs and InGaAs surfaces also takes place for InP. [12][13][14] Sulfur-doped n-type InP (100) 15) a sample treated with ammonium sulfide in 10% (NH 4 ) 2 S in H 2 O for 20 min at room temperature, 16,17) and a sample subjected to a combination of two-stage etching followed by the same ammonium sulfide treatment. The samples were then rinsed in flowing deionized (DI) water for 10 s, blown dry in N 2 and inserted into an ultrahigh vacuum (UHV) system within 7 min.…”

“…15) Prior computational modelling of amorphous 24) and crystalline 25) InP has suggested that P-P and dangling bond species, if present, can lead to deleterious gap states. However, further work in modelling high-k/InP interfaces is needed to establish the correlation of the chemical states observed and potential gap states.…”