InAs-oxide interface composition and stability upon thermal oxidation and high-k atomic layer deposition

Abstract

Defects at the interface between InAs and a native or high permittivity oxide layer are one of the main challenges for realizing III-V semiconductor based metal oxide semiconductor structures with superior device performance. Here we passivate the InAs(100) substrate by removing the native oxide via annealing in ultra-high vacuum (UHV) under a flux of atomic hydrogen and growing a stoichiometry controlled oxide (thermal oxide) in UHV, prior to atomic layer deposition (ALD) of an Al2O3 high-k layer. The semiconductor-oxide interfacial stoichiometry and surface morphology are investigated by synchrotron based X-ray photoemission spectroscopy, scanning tunneling microscopy, and low energy electron diffraction. After thermal oxide growth, we find a thin non-crystalline layer with a flat surface structure. Importantly, the InAs-oxide interface shows a significantly decreased amount of In3+, As5+, and As0 components, which can be correlated to electrically detrimental defects. Capacitance-voltage measurements confirm a decrease of the interface trap density in gate stacks including the thermal oxide as compared to reference samples. This makes the concept of a thermal oxide layer prior to ALD promising for improving device performance if this thermal oxide layer can be stabilized upon exposure to ambient air.

Oxygen relocation during HfO2 ALD on InAs

“…For simplicity, we fitted the data with a single doublet only that includes the contribution of both the As 3+ and As 5+ oxidation states. The presence of an As 5+ suboxide in the native oxide of sample G is not completely unexpected; we have observed it previously 21 , and it is due to the lower homogeneity of the native oxide as compared to the thermal oxide layer.…”

“…2b), measured at a photon energy of 350 eV, is characterized by a dominant doublet at 17.6 eV, corresponding to In bonded to As, and a small shoulder towards high binding energy associated with In oxide (found at 18.1 eV; +0.5 eV from the bulk component); these values are in line with values found elsewhere in literature 8,12,32 . The hydrogen cleaning process should result in an InAs surface without any oxide 21 ; however, clearly this is not the case, but a thin In oxide layer remains. This unexpected behaviour confirms the high stability of the In oxide, as was already observed in our previous studies 8,21 Please do not adjust margins…”

“…The hydrogen cleaning process should result in an InAs surface without any oxide 21 ; however, clearly this is not the case, but a thin In oxide layer remains. This unexpected behaviour confirms the high stability of the In oxide, as was already observed in our previous studies 8,21 Please do not adjust margins…”

“…Hence, it is important to obtain better insight into the details of the initial ALD process, where the influence of the surface plays a significant role. Here, we investigate eight InAs samples prepared with varying oxide thickness ranging from a few Å to a few nanometres by ambient pressure X-ray photoelectron spectroscopy (AP-XPS), a method which allows the real-time monitoring of the deposition process 8,21,22 . We evaluate the influence of the surface on the composition and thickness of the overlayer of HfO 2 already formed during the first half cycle of ALD performed with TDMAHf.…”

Repairing the surface of InAs-based topological heterostructures

“…The native oxide layer in both GaAs and InAs is known to contain a large number of charged defects [39,40], caused by unpaired As atoms within the oxide formed by an excess of As during the oxidation of In and Ga [41,42]. These defects act as scattering sites at the surface of the wafer, and limit the mobility of samples above a certain density.…”