First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

Abstract

Density functional theory paired with a first order many-body perturbation theory correction is applied to determine formation energies and charge transition energies for point defects in bulk In0.53Ga0.47As and for models of the In0.53Ga0.47As/Al2O3 interface. The results are consistent with previous computational studies that AsGa antisites are candidates for defects observed in capacitance voltage measurements on metal-oxide-semiconductor capacitors, as the AsGa antisite introduces energy states near the valence band maximum and near the middle of the energy band gap. However, substantial broadening in the distribution of the GaAs charge transition levels due to the variation in the local chemical environment resulting from alloying on the cation (In/Ga) sublattice is found, whereas this effect is absent for AsGa antisites. Also, charge transition energy levels are found to vary based on proximity to the semiconductor/oxide interface. The combined effects of alloy-and proximity-shift on the GaAs antisite charge transition energies are consistent with the distribution of interface defect levels between the valence band edge and midgap as extracted from electrical characterization data. Hence, kinetic growth conditions leading to a high density of either GaAs or AsGa antisites near the In0.53Ga0.47As/Al2O3 interface are both consistent with defect energy levels at or below midgap.Hence the purpose of the calculations presented in this study is to narrow the possible set of atomistic configurations giving rise to defects levels in the band gap, and thereby motivate the development of growth conditions and processing steps that either passivate the defects or avoid their formation.Recent density functional theory (DFT) investigations of defects in related III-V (GaAs, InAs, and InGaAs alloys) materials have been reported. These studies provide predictions for the stability and amphoteric nature of native defects in bulk and oxide-terminated surface models using hybrid exchange-correlation (XC) functionals [10-14], with the hybrid functionals chosen to overcome the DFT band gap problem. In such approaches a fraction a of Hartree-Fock exchange is mixed into the XC functional (giving rise to a hybrid functional), and the value of a is usually adjusted to reproduce the experimental band gap. These authors [10][11][12][13][14] conclude that the position of the midgap charge transition levels (CTLs) of the AsGa antisite, combined with a predicted lower formation energy relative to other commonly studied point defects, , suggest that this antisite is responsible for the midgap Dit states observed in the capacitance-voltage (CV) response of In0.53Ga0.47As/high-k oxide MOS capacitors. In other works, studies of bonding mechanisms at the III-V/oxide interfaces GaAs/Al2O3 and GaAs/HfO2 have been presented [15], and predictions of charge transition levels (CTLs) of As and P vacancies at (110) oriented GaAs and InP surfaces are reported in ref. [16]. The latter utilizes many body perturbation theory (MBPT) to avoid the need to...

Impact of band to band tunneling in In0.53Ga0.47As tunnel diodes on the deep level transient spectra

“…The origin of the trap state cannot be determined at the moment, and a dedicated study is needed to obtain more information on this trap. Based on ab-initio calculations, also employing the correction of many-body perturbation theory, the H1 trap could be associated with a gallium vacancy level or gallium antisite 15,47,48 .…”