M. Hayes

Electrical characterization of defects introduced during electron beam deposition of Pd schottky contacts on n-type Ge

We have investigated by deep level transient spectroscopy the hole and electron trap defects introduced in n-type Ge during electron beam deposition (EBD) of Pd Schottky contacts. We have also compared the properties of these defects with those introduced in the same material during high-energy electron irradiation. Our results show that EBD introduces several electron and hole traps at and near the surface of Ge. The main defect introduced during EBD has electronic properties similar to those of the V–Sb complex, or E center, introduced during high-energy particle irradiation of Ge. This defect has two levels E0.38 and H0.30 that correspond to its (−−,−) and (−,0) charge states.

Electrical and structural characterization of as-grown and annealed hydrothermal bulk ZnO

Hall effect measurements in the range 20–370 K on as-grown and annealed hydrothermal bulk ZnO have been performed. The bulk conductivity in the highly resistive as-grown sample was found to decrease and then increase after annealing at 550 °C and 930 °C, respectively. The conduction in the as-grown material is attributed to a deep donor which is replaced by a much shallower donor after annealing at 930 °C. Annealing at both temperatures also produced strong surface conduction effects. Nondegenerate low-mobility surface conduction dominated the electrical properties of the sample annealed at 550 °C, while a degenerate surface channel was formed after annealing at 930 °C. In addition, Rutherford backscattering and channeling spectrometry (RBS/C) was used to assess the effect of annealing on the crystalline quality of the samples. RBS/C measurements reveal that annealing at 930 °C leads to significant improvement of the crystalline quality of the material, while annealing at 550 °C results in the segregation...

Range parameters of gold and lead in carbon and carbon in gold at reduced energies of 10−3 < ϵ < 1

Abstract Mean projected ranges and range straggling widths were determined for implants of Au and Pb into C at energies of about 1–1000 keV and for C into Au between 5 and 40 keV. The respective impurity depth profiles were obtained by backscattering of α-particles and the 13C(p,γ)-resonance reaction at 1.75 MeV. The range data of Au C are about 10% higher than TRIM at LSS energies ϵ Pb C . At ϵ ∼ 1 about 50% higher ranges are found for both systems. The straggling widths grossly exceed TRIM estimates at all energies. In contrast, TRIM correctly predicts both range moments for the reverse system C Au . The results are readily explained by Z1 variations of nuclear stopping at low energies and by reduced electronic stopping at high energies for Au C and Pb C , whereas correlation effects between the two stopping mechanisms seem to be of minor importance.

Electrical characterization of defects introduced in n-type Ge during indium implantation

The authors have employed deep level transient spectroscopy to investigate the defects introduced in n-type Ge during 160keV indium (In) ion implantation. Our results show that In implantation introduces three prominent electron traps with energy levels at EC−0.09eV, EC−0.15eV, and EC−0.30eV, respectively. The authors have found that these defects are different from the point defects introduced by electron irradiation but that they do not involve In. Annealing at 600°C removed all the defects introduced during In implantation but results in a single prominent defect with a level at EC−0.35eV.

Electrical characterisation of epitaxially grown n-GaN bombarded with high- and low-energy protons

Abstract Using deep-level transient spectroscopy (DLTS), we have found that 1 MeV proton bombardment introduces the ER3, nitrogen vacancy related defect, at a rate of 290±50 cm −1 . Further, using capacitance–voltage (C–V) measurements, we have found that 1 MeV protons remove free carriers at a rate of 3880±380 cm −1 . However, when bombarding GaN with 0.5 keV protons, we did not observe the ER3 defect. We propose that 0.5 keV protons indeed introduce the ER3 defect, but that it is passivated by hydrogen.

Thermal Stability of Ti/Mo Schottky Contacts on p-Si and Defects Introduced in p-Si during Electron Beam Deposition of Ti/Mo

In this study we have investigated the thermal stability (in the range 100 oC - 900 oC) of defects introduced in p-Si by electron beam deposition (EBD) of Ti and Ti/Mo Schottky contacts. The depletion regions below these contacts were probed by conventional deep level transient spectroscopy (DLTS) as well as Laplace (high-resolution) DLTS (L-DLTS). We have chosen Ti as the Schottky contact because the barrier height of Ti/p-Si (0.53 eV) is close to that of TiSi2/p-Si (0.50 eV) that forms after annealing at 600 – 650 oC. The Mo was added on top of the Ti in order to prevent annealing degradation. These contacts were annealed in Ar at temperatures of up to 900 oC in 100 oC steps for half-hour periods. Current – voltage (I-V) and capacitance – voltage (C-V) measurements were used to monitor the quality of the Schottky contacts. DLTS was performed after each annealing cycle to monitor the presence of the EBD-induced defects and to obtain heir electronic properties. We have found that that the Ti/Mo contacts were superior to the Ti contacts. Their (Ti/Mo) barrier height after EBD was 0.52 eV and it gradually increased to 0.56 eV after annealing at 500 oC - 600oC and then dropped to 0.50 eV annealing at 700 oC. DLTS revealed that the main defects introduced during metallization are hole traps H(0.17), H(0.23), H(0.37) and H(0.49). Annealing at 350 oC introduced an additional hole trap H(0.39). After annealing at 550 oC all defects were removed from the depletion region.

Electron traps created in n-type GaN during 25 keV hydrogen implantation

We have implanted Ni/n-GaN Schottky contacts with 25 keV hydrogen ions (protons). The defects, thus, introduced were studied using deep level transient spectroscopy. We have found that 25 keV proton implantation introduces a complex set of electron traps in GaN, of which most are different to the defects observed after high-energy (MeV) electron and proton implantation. Two prominent defects that could clearly be distinguished from each other have energy levels at 0.22 and 0.30 eV below the conduction band. At least three of the defects detected after 25 keV proton implantation exhibit a metastable character in which they can be reproducibly removed and re-introduced during reverse and zero bias anneal cycles.

Electronic properties of shallow level defects in ZnO grown by pulsed laser deposition

We have used deep level transient spectroscopy (DLTS) to characterise four defects with shallow levels in ZnO grown by pulsed laser deposition (PLD). These defects all have DLTS peaks below 100 K From DLTS measurements and Arrhenius plots we have calculated the energy levels of these defects as 31 meV, 64 meV, 100 meV and 140 meV, respectively, below the conduction band. The 100 meV defect displayed metastable behaviour: Annealing under reverse bias at temperatures of above 130 K introduced it while annealing under zero bias above 110 K removed it. The 64 meV and 140 meV defects exhibited a strong electric field assisted emission, indicating that they may be donors.

Low cost solar grade silicon by recycling cast ingot rejects

There is a measure of agreement that Solar Grade Silicon (SGS) with a purity of 99.9999% [6N] can be manufactured using low cost processes and used to make commercially valuable solar cells, thus helping to achieve Grid Parity using crystalline silicon technology. A preferred approach is the use of Metallurgical Grade Silicon (MGSi) as raw material for SGS. In this work, we describe the potential for using silicon obtained by recycling a variety of silicon rejects from various Photovoltaic and Semiconductor manufacturing operations.

Low cost, low CO 2 emission solar grade silicon

The OSE Process is capable of achieving low SGS manufacturing cost in a manner consistent with low SEC and low CO2 emissions. In addition to the promise of the UMG process in helping to achieve the appropriate low cost for crystalline silicon modules consistent with grid parity, low CO2 emissions can become an additional driving force for SGS use in the PV industry.