Optical signatures of deep level defects in Ga2O3

Abstract

We used depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy to measure the effects of near-surface plasma processing and neutron irradiation on native point defects in β-Ga2O3. The near-surface sensitivity and depth resolution of these optical techniques enabled us to identify spectral changes associated with removing or creating these defects, leading to identification of one oxygen vacancy-related and two gallium vacancy-related energy levels in the β-Ga2O3 bandgap. The combined near-surface detection and processing of Ga2O3 suggests an avenue for identifying the physical nature and reducing the density of native point defects in this and other semiconductors.

Hydrogen plasma treatment of β -Ga2O3: Changes in electrical properties and deep trap spectra

“…25,26 The most likely candidates seem to be deep acceptors with the optical ionization threshold near 2.3 eV and 3.4 eV. 25,26,29 Their presence in very high concentration is not confirmed in our high temperature/low frequency C-V measurements with illumination. The proposed hydrogen passivation of donors would be in contrast to theoretical predictions and to some experimental results obtained for H introduction at high temperatures during growth.…”

Impact of deep level defects induced by high energy neutron radiation in β-Ga2O3

“…12 There has been a recent report on neutron irradiation effects using depth-resolved cathodoluminescence and surface photovoltage spectroscopy to explore optical defect transitions >1.1 eV within the β-Ga 2 O 3 bandgap. 19 Here, we use a combination of DLTS and deep level optical spectroscopy (DLOS) to quantify the energy levels and concentration distributions of defect states throughout the ∼4.8 eV bandgap of unintentionally doped (UID) β-Ga 2 O 3 substrates grown by the EFG method, before and after neutron irradiation at several doses. The specific neutron irradiation-induced defect states causing carrier removal via a compensation mechanism are identified, and the evolution of the deep level defect distribution for two displacement damage doses of neutron radiation is compared and quantified using DLTS and DLOS.…”

Kinetics of charge carrier recombination in β−Ga2O3 crystals

“…An alternative explanation for the n-type conductivity is from the inadvertent incorporation of impurities, especially Sn or H, that act as shallow donors [5]. Additionally, theoretical and experimental studies have suggested that gallium vacancies (V Ga ) are native acceptors and are responsible for the compensation of n-type conductivity [7][8][9]. Recently, substitutional Fe at Ga sites (Fe Ga ) has been found to be an energetically favorable acceptor defect in edge-defined film-fed grown (EFG) β-Ga 2 O 3 crystals, which dominates deep-level defect traps [10].…”

“…Computational and electron paramagnetic resonance (EPR) studies clearly demonstrated that self-trapped holes are thermally stable in β-Ga 2 O 3 [16,17], which serve as a precursor for the formation of self-trapped excitons (STEs) that are responsible for the dominant UV emission in β-Ga 2 O 3 single crystals [3,15]. The BL emission has been found to be strong in conducting Ga 2 O 3 samples and as a result has been assigned to the recombination of an electron bound to a V O defect [3,9,14], Several Ga 2 O 3 -based devices have been reported with an optical response in the UV range that exhibit a dramatic change in the electronic transport with increasing operation temperature [2,18], indicating the importance of controlling and understanding temperaturedependent carrier recombination kinetics in Ga 2 O 3 . In this paper we investigate characteristics of luminescence bands in Ga 2 O 3 and provide evidence of the involvement of carrier trapping in an electron injection-induced optical emission.…”