A. Venter - Academia.edu (original) (raw)

Papers by A. Venter

physica status solidi (c), 2008

ABSTRACT The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. T... more ABSTRACT The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. The electrical properties of Sn doped InAs films grown on semi-insulating GaAs substrates by MOVPE are extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that Sn concentrations can be controlled over 2 orders of magnitude. The Sn doped InAs layers exhibit carrier concentrations between 2.7 x 1017 and 4.7 x 1019 cm–3 with 77 K mobilities ranging from 12 000 to 1300 cm2/Vs. Furthermore, the influence of the variation of these parameters on the structural properties of InAs are also reported. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Physica B: Condensed Matter, 2012

The electronic properties of defects introduced by low energy inductively coupled Ar plasma etchi... more The electronic properties of defects introduced by low energy inductively coupled Ar plasma etching of n-type (Si doped) GaAs were investigated by deeplevel transient spectroscopy (DLTS) and Laplace DLTS. Several prominent electron traps (E c-0.046 eV, E c-0.186 eV, E c-0.314 eV. E c-0.528 eV and E c-0.605 eV) were detected. The metastable defect E c-0.046 eV having a trap signature similar to E1 is observed for the first time. E c-0.314 eV and E c-0.605 eV are metastable and appear to be similar to the M3 and M4 defects present in dc H-plasma exposed GaAs.

Physica B: Condensed Matter, 2009

Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O 2 atmosphere. The a... more Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O 2 atmosphere. The anneal temperature and time were 450 1C and 2.5 h, respectively. X-ray diffraction of the oxidized Ni/InAs sample revealed the formation of In 3 Ni 2 and In 2 O 3 on the front suggesting inter diffusion of In, Ni and O. NiO was not detected by X-ray diffraction. In a preliminary study, using glass as a substrate, NiO readily formed when using these oxidation parameters. Conductivity measurements of the oxidized Ni/InAs surface revealed a conducting front and insulating rear surface while TEM of the Ni/InAs interface revealed an intermediate amorphous diffusion zone between the ''oxidized'' Ni layer and the bulk InAs. A closer investigation of the intermediate layer supports the X-ray diffraction results, suggesting compound formation due to diffusion of oxygen and nickel into the substrate, and out-diffusion of In and As from the bulk of the sample. AES was used to further elucidate these results.

Physica B: Condensed Matter, 2012

ABSTRACT Bulk (100) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4... more ABSTRACT Bulk (100) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (ϕb) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at −0.2V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb–O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5nm.

Journal of Crystal Growth, 2007

Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-typ... more Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-type behaviour for p-type samples, especially at very low doping concentrations. A two-layer model is presented which can potentially be used to extract the bulk layer properties of a semiconductor epilayer. We here apply this model to two different materials, InAs and InAsSb, and extract their transport properties.

Journal of Applied Physics, 2012

Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 ... more Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 Â 10 14 cm À3 and 2.5 Â 10 15 cm À3 were exposed to a dc-hydrogen or helium plasma. Hydrogen exposure resulted in the introduction of a single prominent defect level at E C À0.31 eV. Exposing similar samples to He plasmas introduced the same electron trap. The trap concentration increased linearly with dopant concentration suggesting that Sb may be a component of this plasma-induced trap. Thermal annealing kinetics studies suggested that this defect anneals out by diffusion.

Journal of Applied Physics, 2012

Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E c-0.04 eV, E c-0... more Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E c-0.04 eV, E c-0.07 eV, E c-0.19 eV, E c-0.31 eV, E c-0.53 eV, and E c-0.61 eV). The trap, E c-0.04 eV, labelled E1 0 and having a trap signature similar to irradiation induced defect E1, appears to be metastable. E c-0.31 eV and E c-0.61 eV are metastable too and they are similar to the M3/M4 defect configuration present in hydrogen plasma exposed n-GaAs. V

Diamond and Related Materials, 1994

Diamond films have been deposited on Si(001) by hot-filament chemical vapour deposition and chara... more Diamond films have been deposited on Si(001) by hot-filament chemical vapour deposition and characterized by transmission and scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The temperature of the filament was found to be the critical factor determining whether polycrystalline diamond, polycrystalline tungsten or diamond layers contaminated with tungsten were deposited. The effect of surface roughening on the nucleation density of the diamond particles was also investigated.

Physica B: Condensed Matter, 2011

Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defe... more Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1 x 10 13 protons/cm 2. The results show that proton irradiation resulted in primary hole traps at E V + 0.15 eV and E V + 0.30 eV and electron traps, at E C-0.38 eV, E C-0.32 eV, E C-0. 31 eV, E C-0.22 eV, E C-0.20 eV, E C-0.17 eV, E C-0.15 eV and E C-0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C-0.31 eV, E C-0.17 eV and, E C-0.04 eV, and E V + 0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.

Physica B: Condensed Matter, 2011

Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defe... more Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1 x 10 13 protons/cm 2 . The results show that proton irradiation resulted in primary hole traps at E V + 0.15 eV and E V + 0.30 eV and electron traps, at E C -0.38 eV, E C -0.32 eV, E C -0. 31 eV, E C -0.22 eV, E C -0.20 eV, E C -0.17 eV, E C -0.15 eV and E C -0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C -0.31 eV, E C -0.17 eV and, E C -0.04 eV, and E V + 0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.

physica status solidi (c), 2008

ABSTRACT The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. T... more ABSTRACT The feasibility of tetraethyl tin (TESn) as an n-type dopant for InAs is investigated. The electrical properties of Sn doped InAs films grown on semi-insulating GaAs substrates by MOVPE are extensively studied as a function of substrate temperature, V/III ratio, substrate orientation and TESn flow rate. Results from this study show that Sn concentrations can be controlled over 2 orders of magnitude. The Sn doped InAs layers exhibit carrier concentrations between 2.7 x 1017 and 4.7 x 1019 cm–3 with 77 K mobilities ranging from 12 000 to 1300 cm2/Vs. Furthermore, the influence of the variation of these parameters on the structural properties of InAs are also reported. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Physica B: Condensed Matter, 2012

The electronic properties of defects introduced by low energy inductively coupled Ar plasma etchi... more The electronic properties of defects introduced by low energy inductively coupled Ar plasma etching of n-type (Si doped) GaAs were investigated by deeplevel transient spectroscopy (DLTS) and Laplace DLTS. Several prominent electron traps (E c-0.046 eV, E c-0.186 eV, E c-0.314 eV. E c-0.528 eV and E c-0.605 eV) were detected. The metastable defect E c-0.046 eV having a trap signature similar to E1 is observed for the first time. E c-0.314 eV and E c-0.605 eV are metastable and appear to be similar to the M3 and M4 defects present in dc H-plasma exposed GaAs.

Physica B: Condensed Matter, 2009

Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O 2 atmosphere. The a... more Ni was resistively deposited onto bulk InAs and subsequently oxidized in an O 2 atmosphere. The anneal temperature and time were 450 1C and 2.5 h, respectively. X-ray diffraction of the oxidized Ni/InAs sample revealed the formation of In 3 Ni 2 and In 2 O 3 on the front suggesting inter diffusion of In, Ni and O. NiO was not detected by X-ray diffraction. In a preliminary study, using glass as a substrate, NiO readily formed when using these oxidation parameters. Conductivity measurements of the oxidized Ni/InAs surface revealed a conducting front and insulating rear surface while TEM of the Ni/InAs interface revealed an intermediate amorphous diffusion zone between the ''oxidized'' Ni layer and the bulk InAs. A closer investigation of the intermediate layer supports the X-ray diffraction results, suggesting compound formation due to diffusion of oxygen and nickel into the substrate, and out-diffusion of In and As from the bulk of the sample. AES was used to further elucidate these results.

Physica B: Condensed Matter, 2012

ABSTRACT Bulk (100) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4... more ABSTRACT Bulk (100) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (ϕb) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at −0.2V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb–O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5nm.

Journal of Crystal Growth, 2007

Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-typ... more Strong surface inversion usually leads to deceptive Hall measurements by reflecting typical n-type behaviour for p-type samples, especially at very low doping concentrations. A two-layer model is presented which can potentially be used to extract the bulk layer properties of a semiconductor epilayer. We here apply this model to two different materials, InAs and InAsSb, and extract their transport properties.

Journal of Applied Physics, 2012

Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 ... more Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 Â 10 14 cm À3 and 2.5 Â 10 15 cm À3 were exposed to a dc-hydrogen or helium plasma. Hydrogen exposure resulted in the introduction of a single prominent defect level at E C À0.31 eV. Exposing similar samples to He plasmas introduced the same electron trap. The trap concentration increased linearly with dopant concentration suggesting that Sb may be a component of this plasma-induced trap. Thermal annealing kinetics studies suggested that this defect anneals out by diffusion.

Journal of Applied Physics, 2012

Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E c-0.04 eV, E c-0... more Ar plasma etching of n-type (Si doped) GaAs introduces several electron traps (E c-0.04 eV, E c-0.07 eV, E c-0.19 eV, E c-0.31 eV, E c-0.53 eV, and E c-0.61 eV). The trap, E c-0.04 eV, labelled E1 0 and having a trap signature similar to irradiation induced defect E1, appears to be metastable. E c-0.31 eV and E c-0.61 eV are metastable too and they are similar to the M3/M4 defect configuration present in hydrogen plasma exposed n-GaAs. V

Diamond and Related Materials, 1994

Diamond films have been deposited on Si(001) by hot-filament chemical vapour deposition and chara... more Diamond films have been deposited on Si(001) by hot-filament chemical vapour deposition and characterized by transmission and scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The temperature of the filament was found to be the critical factor determining whether polycrystalline diamond, polycrystalline tungsten or diamond layers contaminated with tungsten were deposited. The effect of surface roughening on the nucleation density of the diamond particles was also investigated.

Physica B: Condensed Matter, 2011

Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defe... more Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1 x 10 13 protons/cm 2. The results show that proton irradiation resulted in primary hole traps at E V + 0.15 eV and E V + 0.30 eV and electron traps, at E C-0.38 eV, E C-0.32 eV, E C-0. 31 eV, E C-0.22 eV, E C-0.20 eV, E C-0.17 eV, E C-0.15 eV and E C-0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C-0.31 eV, E C-0.17 eV and, E C-0.04 eV, and E V + 0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.

Physica B: Condensed Matter, 2011

Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defe... more Deep level transient spectroscopy (DLTS), and Laplace-DLTS have been used to investigate the defects created in Sb doped Ge after irradiation with 2 MeV protons having a fluence of 1 x 10 13 protons/cm 2 . The results show that proton irradiation resulted in primary hole traps at E V + 0.15 eV and E V + 0.30 eV and electron traps, at E C -0.38 eV, E C -0.32 eV, E C -0. 31 eV, E C -0.22 eV, E C -0.20 eV, E C -0.17 eV, E C -0.15 eV and E C -0.04 eV. Defects observed in this study are compared with those introduced in similar samples after MeV electron irradiation reported earlier. E C -0.31 eV, E C -0.17 eV and, E C -0.04 eV, and E V + 0.15 eV were not observed previously in similar samples after high energy irradiation. Results from this study suggest that although similar defects are introduced by electron and proton irradiation, traps introduced by the latter are dose dependent.