Annealing and surface conduction on hydrogen peroxide treated bulk melt grown, single crystal ZnO

We report on the studies carried out on hydrogen peroxide treated melt grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8 ± 0.3) meV that has been suggested as Zni related and possibly H-complex related and (54.5 ± 0.9) meV which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, XZn. The surface donor volume concentration of the conductive channel was calculated from theory developed by D. C. Look [1]. Results indicate an increase in surface volume concentration with increasing annealing temperature from 6.0´1017 cm-3 at 200°C to 4.37´1018 cm-3 at 800°C.South African National Research Foundationhttp://www.elsevier.com/locate/physbhb2013ai201

Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (1 0 0)

Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (100) Sbdoped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (100) was observed up to annealing temperature of 500oC. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (100) system occurs between 600-700oC.This work has been made possible by financial assistance from the South African National Research Foundation.http://www.elsevier.com/locate/jallcomnf201

Thermal annealing behaviour of Pd Schottky contacts on melt-grown single crystal ZnO studied by IV and CV measurements

Current–voltage (IV) and capacitance–voltage (CV) measurement techniques have successfully been employed to study the effects of annealing highly rectifying Pd/ZnO Schottky contacts. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at −1.5 V. An average barrier height of (0.77 ± 0.02) eV has been calculated by assuming pure thermionic emission for the as-deposited material and as (0.56 ± 0.03) eV after annealing at 550 ◦C. The reverse current has been measured as (2.10 ± 0.01) × 10−10 A for the as-deposited and increases by 5 orders of magnitude after annealing at 550 ◦C to (1.56 ± 0.01) × 10−5 A. The depletion layer width measured at −2.0 V has shown a strong dependence on thermal annealing as it decreases from 1.09 m after annealing at 200 ◦C to 0.24 m after annealing at 500 ◦C, resulting in the modification of the dopant concentration within the depletion region and hence the current flowing through the interface from pure thermionic emission to thermionic field emission with the donor concentrations increasing from 6.90 × 1015 cm−3 at 200 ◦C to 6.06 × 1016 cm−3 after annealing at 550 ◦C. This increase in the volume concentration has been explained as an effect of a conductive channel that shifts closer to the surface after sample annealing. The series resistance has been observed to decrease with increase in annealing temperature. The Pd contacts have shown high stability up to an annealing temperature of 250 ◦C as revealed by the IV and CV characteristics after which the quality of the contacts deteriorates with increase in annealing temperature.http://www.elsevier.com/locate/msebhb201

Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8±0.3) meV that has been suggested as Zni related and possibly H-complex related and (54.5±0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, XZn. The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) [1]. Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60×1017 cm−3 at 200 °C to 4.37×1018 cm-3 at 800 °C

Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (1 0 0)

Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current–voltage (I–V) and capacitance–voltage (C–V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 °C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 °C

The dependence of barrier height on temperature for Pd Schottky contacts on ZnO

Temperature dependent current–voltage (I–V) and capacitance–voltage (C–V) measurements have been performed on Pd/ZnO Schottky barrier diodes in the range 60–300 K. The room temperature values for the zero bias barrier height from the I–Vmeasurements (ΦI–V) was found to be 0.52 eV and from the C–V measurements (ΦC–V) as 3.83 eV. From the temperature dependence of forward bias I–V, the barrier height was observed to increase with temperature, a trend that disagrees with the negative temperature coefficient for semiconductor material. The C–V barrier height decreases with temperature, a trend that is in agreement with the negative temperature coefficient of semiconductor material. This has enabled us to fit two curves in two regions (60–120 K and 140–300 K). We have attributed this behaviour to a defect observed by DLTS with energy level 0.31 eV below the conduction band and defect concentration of between 4×1016 and 6×1016 cm−3 that traps carriers, influencing the determination of the barrier height

Thermal annealing behaviour of Pd Schottky contacts on melt-grown single crystal ZnO studied by IV and CV measurements

Current–voltage (IV) and capacitance–voltage (CV) measurement techniques have successfully been employed to study the effects of annealing highly rectifying Pd/ZnO Schottky contacts. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at −1.5 V. An average barrier height of (0.77 ± 0.02) eV has been calculated by assuming pure thermionic emission for the as-deposited material and as (0.56 ± 0.03) eV after annealing at 550 ◦C. The reverse current has been measured as (2.10 ± 0.01) × 10−10 A for the as-deposited and increases by 5 orders of magnitude after annealing at 550 ◦C to (1.56 ± 0.01) × 10−5 A. The depletion layer width measured at −2.0 V has shown a strong dependence on thermal annealing as it decreases from 1.09 m after annealing at 200 ◦C to 0.24 m after annealing at 500 ◦C, resulting in the modification of the dopant concentration within the depletion region and hence the current flowing through the interface from pure thermionic emission to thermionic field emission with the donor concentrations increasing from 6.90 × 1015 cm−3 at 200 ◦C to 6.06 × 1016 cm−3 after annealing at 550 ◦C. This increase in the volume concentration has been explained as an effect of a conductive channel that shifts closer to the surface after sample annealing. The series resistance has been observed to decrease with increase in annealing temperature. The Pd contacts have shown high stability up to an annealing temperature of 250 ◦C as revealed by the IV and CV characteristics after which the quality of the contacts deteriorates with increase in annealing temperature.http://www.elsevier.com/locate/msebhb201