@misc{AdelmannCuypersTallaridaetal., author = {Adelmann, Christoph and Cuypers, Daniel and Tallarida, Massimo and Rodriguez, Leonard and De Clercq, Astrid and Friedrich, Daniel and Conard, Thierry and Delabie, Annelies and Seo, Jin Won and Locquet, Jean-Pierre and De Gendt, Stefan and Schmeißer, Dieter and Elshocht, Sven van and Caymax, Matty}, title = {Surface Chemistry and Interface Formation during the Atomic Layer Deposition of Alumina from Trimethylaluminum and Water on Indium Phosphide}, series = {Chemistry of Materials}, volume = {25}, journal = {Chemistry of Materials}, number = {7}, issn = {1520-5002}, doi = {10.1021/cm304070h}, pages = {1078 -- 1091}, abstract = {The surface chemistry and the interface formation during the initial stages of the atomic layer deposition (ALD) of Al2O3 from trimethylaluminum (TMA) and H2O on InP(100)were studied by synchrotron radiation photoemission spectroscopy and scanning tunneling microscopy. The effect of the ex situ surface cleaning by either H2SO4 or (NH4)2S was examined. It is shown that the native oxide on the InP surface consisted mainly of indium hydrogen phosphates with a P enrichment at the interface with InP. After a (NH4)2S treatment, S was present on the surface as a sulfide in both surface and subsurface sites. Exposure to TMA led to the formation of a thin AlPO4 layer, irrespective of the surface cleaning. The surface Fermi level of p-type InP was found to be pinned close to midgap after H2SO4 cleaning and moved only slightly further toward the conduction band edge upon TMA exposure, indicating that the AlPO4/InP interface was rather defective. (NH4)2S passivation led to a Fermi level position of p-type InP close to the conduction band edge. Hence, the InP surface was weakly inverted, which can be attributed to surface doping by S donors. TMA exposure was found to remove surface S, which was accompanied by a shift of the Fermi level to midgap, consistent with the removal of (part of) the S donors in combination with a defective AlPO4/InP interface. Further TMA/H2O ALD did not lead to any detectable changes of the AlPO4/InP interface and suggested simple overgrowth with Al2O3.}, language = {en} } @misc{DorpNynsCuypersetal., author = {Dorp, Dennis H. von and Nyns, Laura and Cuypers, Daniel and Ivanov, Tsvetan and Brizzi, Simone and Tallarida, Massimo and Fleischmann, Claudia and H{\"o}nicke, Philipp and M{\"u}ller, Matthias and Richard, Olivier and Schmeißer, Dieter and De Gendt, Stefan and Lin, Dennis H. C. and Adelmann, Christoph}, title = {Amorphous Gadolinium Aluminate as a Dielectric and Sulfur for Indium Phosphide Passivation}, series = {ACS Applied Electronic Materials}, volume = {1}, journal = {ACS Applied Electronic Materials}, number = {11}, issn = {2637-6113}, doi = {10.1021/acsaelm.9b00388}, pages = {2190 -- 2201}, abstract = {The passivation of n-type InP (100) using sulfur in combination with a gadolinium aluminate (GAO) dielectric layer has been studied. Photoluminescence, minority-carrier lifetime, and capacitance-voltage measurements indicate that a (NH4)2S vapor passivation step prior to atomic layer deposition of the oxide effectively lowers the interface state density. Surface and interface chemistry were studied by synchrotron radiation photoemission spectroscopy (SRPES). The effect of ex situ surface passivation after native oxide removal in HCl solution was examined. It was observed that surface reoxidation occurred during (NH4)2S vapor exposure, leading to the formation of Inx(HPO4)y. S was present on the surface as a sulfide in both surface and subsurface sites. After atomic layer deposition of GAO, sulfates were detected in addition to Inx(HPO4)y, which was confirmed by near-edge X-ray absorptionfine structure analysis. The S in the stack was quantified using reference-free grazing incidence X-rayfluorescence analysis. X-ray absorption spectroscopy showed that Gd was oxidized and present in the 3+ oxidation state, most likely as a phosphate close to the InP interface and possibly mixed with sulfates. Energy-dependent SRPES measurements of Al 2p and Gd 4d core levels, complemented by transmission electron microscopy, further suggest that the dielectric layer was segregated. Valence band measurements confirm the effective passivation of InP, indicating unpinning of the surface Fermi level.}, language = {en} } @misc{CuypersFleischmannDorpetal., author = {Cuypers, Daniel and Fleischmann, Claudia and Dorp, Dennis H. von and Brizzi, Simone and Tallarida, Massimo and M{\"u}ller, Matthias and H{\"o}nicke, Philipp and Billen, Arne and Chintala, Ravi and Conard, Thierry and Schmeißer, Dieter and Vandervorst, Wilfried and Elshocht, Sven van and Armini, Silvia and De Gendt, Stefan and Adelmann, Christoph}, title = {Sacrificial Self-Assembled Monolayers for the Passivation of GaAs(100) Surfaces and Interfaces}, series = {Chemistry of Materials}, volume = {28}, journal = {Chemistry of Materials}, number = {16}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.6b01732}, pages = {5689 -- 5701}, abstract = {The use of sacrificial self-assembled monolayers (SAMs) to prepare clean n-type GaAs (100) surfaces without band bending in vacuo is demonstrated. GaAs surface passivation using octadecanethiol SAMs after HCl cleaning is shown to lead to an enhancement of the room-temperature photoluminescence intensity. Synchrotron-radiation photoelectron spectroscopy (SRPES) finds that the interfacial oxide between GaAs and the SAM remains below the detection limit. Evidence for both Ga-S and As-S bonds at the GaAs-thiolate interface is found. The limited thermal stability of the SAM allows the desorption of the alkyl chains by in situ thermal annealing at temperatures above 180 °C, leaving S bonded to Ga behind. The resulting surface contains only a very small amount of O (0.05 ML coverage) and C (about 3\% of the SAM remaining) and shows no band bending with the surface Fermi level close to the conduction band. Atomic layer deposition of Al₂O₃ on this surface occurs via the formation of Al-S bonds without introducing any additional band bending. This indicates that the surface preparation of n-type GaAs (100) using sacrificial octadecanethiol SAMs followed by in situ thermal removal provides a route toward GaAs/oxide interfaces without interfacial oxides and without band bending.}, language = {en} } @misc{CuypersDorpTallaridaetal., author = {Cuypers, Daniel and Dorp, Dennis H. von and Tallarida, Massimo and Brizzi, Simone and Conard, Thierry and Rodriguez, Leonard and Mees, M. and Arnauts, Sophia and Schmeißer, Dieter and Adelmann, Christoph and De Gendt, Stefan}, title = {Study of InP Surfaces after Wet Chemical Treatments}, series = {ECS Journal of Solid State Science and Technology}, volume = {3}, journal = {ECS Journal of Solid State Science and Technology}, number = {1}, issn = {2162-8777}, doi = {10.1149/2.005401jss}, pages = {N3016 -- N3022}, abstract = {The influence of different wet chemical treatments (HCl, H₂SO₄, NH₄OH) on the composition of InP surfaces is studied by using synchrotron radiation photoemission spectroscopy (SRPES). It is shown that a significant amount of oxide remains present after immersion in a NH₄OH solution which is ascribed to the insolubility of In³⁺ at higher pH values. Acidic treatments efficiently remove the native oxide, although components like Pᴼ, Inᴼ and P(2±Δ)+ suboxides are observed. Alternatively, the influence of a passivation step in (NH₄)₂S solution on the surface composition was investigated. The InP surface after immersion into (NH₄)₂S results in fewer surface components, without detection of Pᴼ and P(2±Δ)+ suboxides. Finally, slight etching of InP surfaces in HCl/H₂O₂ solution followed by a native oxide removal step, showed no significant effect on the surface composition.}, language = {en} } @misc{CuypersDorpTallaridaetal., author = {Cuypers, Daniel and Dorp, Dennis H. von and Tallarida, Massimo and Brizzi, Simone and Rodriguez, Leonard and Conard, Thierry and Arnauts, Sophia and Schmeißer, Dieter and Adelmann, Christoph and De Gendt, Stefan}, title = {Study of InP Surfaces after Wet Chemical Treatments}, series = {ECS Transactions}, volume = {58}, journal = {ECS Transactions}, number = {6}, issn = {1938-6737}, doi = {10.1149/05806.0297ecst}, pages = {297 -- 303}, abstract = {In this work synchrotron radiation photoemission spectroscopy (SRPES) is used to study InP surfaces after different wet chemical treatments. All results are compared to a typical fingerprint of surface components present on an as received InP sample. It is shown that acidified (HCl and H₂SO₄) treatments efficiently remove the native phosphate, although components like Pᴼ, Inᴼ and P(2±∆)+ remain present. In alkaline solution (NH₄OH) oxide remains present at the surface. As an alternative treatment, the immersion into (NH₄)₂S was studied. This passivation treatment results in fewer surface components which suggests that a higher quality surface is obtained.}, language = {en} } @inproceedings{CuypersDorpTallaridaetal., author = {Cuypers, Daniel and Dorp, Dennis H. von and Tallarida, Massimo and Brizzi, Simone and Rodriguez, Leonard and Conard, Thierry and Arnauts, Sophia and Schmeißer, Dieter and Adelmann, Christoph and De Gendt, Stefan}, title = {Study of InP Surfaces After Wet Chemical Treatments}, series = {Meeting Abstracts-Electrochemical Society, San Francisco, 2013}, booktitle = {Meeting Abstracts-Electrochemical Society, San Francisco, 2013}, publisher = {The Electrochemical Society}, pages = {S. 2132}, language = {en} }