C. Nyamhere

Electrical characterisation and predictive simulation of defects induced by keV Si+ implantation in n-type Si

In this work, we focused on the analysis of implantation-induced defects, mainly small interstitial clusters (ICs) and {311} defects introduced in n-type Si after ion implantation using deep level transient spectroscopy (DLTS). Silicon ions (at 160 keV or 190 keV) of fluences ranging from (0.1–8.0) × 1013 cm−2 have been implanted into n-type Si and annealed at temperatures between 500 °C and 800 °C specifically to create small ICs or {311}s rod-like defects. In samples dominated by small ICs, DLTS spectra show prominent deep levels at Ec − 0.24 eV and Ec − 0.54 eV. After increasing the fluence and temperature, i.e., reducing the number of small ICs and forming {311} defects, the peak Ec − 0.54 eV is still dominant while other electron traps Ec − 0.26 eV and Ec − 0.46 eV are introduced. There were no observable deep levels in reference, non-implanted samples. The identity and origin of all these traps are interpreted in conjunction with recently developed predictive defect simulation models.

Characterization of the E(0.31) defect introduced in bulk n-Ge by H or He plasma exposure

Bulk antimony (Sb) doped germanium (n-Ge) samples with doping concentrations ranging between 7.0 × 1014 cm−3 and 2.5 × 1015 cm−3 were exposed to a dc-hydrogen or helium plasma. Hydrogen exposure resulted in the introduction of a single prominent defect level at EC −0.31 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.

Ar plasma induced deep levels in epitaxial n-GaAs

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

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.

Electrical characterization of {311} defects and related junction leakage currents in n-type Si after ion implantation

A special fabrication process involving chemical vapor deposition (CVD) was designed in order to fabricate advanced structures used to successfully investigate both deep level transient spectroscopy (DLTS) and leakage currents related to the defects on the same test structures. Silicon ions of energy 160 keV and doses 1.0 × 1012 cm−2, 1.0 × 1013 cm−2 and 8.0 × 1013 cm−2 have been implanted into n-type Si substrate and annealed at 800°C. The highest dose was specifically used to create rod-like {311} extended defects. DLTS spectra show prominent electron traps at EC - 0.26 eV, EC - 0.46 eV and EC - 0.54 eV. There were no observable deep levels in the un-implanted (reference) samples. The identity and origin of all these traps will be interpreted in conjunction with annealing studies, literature results and recently developed predictive defect simulation models. The junction leakage current is found to slightly increase in the presence of {311} defects, which shows that their presence does not significantly...

Deep level transient spectroscopy characterization of defects introduced in p-Si by electron beam deposition and proton irradiation

A study of defects introduced during metalisation by electron beam deposition (EBD) process and those introduced by MeV proton irradiation of boron doped p-type Cz grown silicon is presented. We have observed the following hole traps at, 0.32 ± 0.01 eV and 0.54 ± 0.01 eV above the valence band, induced during EBD processing of Titanium/Molybdenum (Ti/Mo) Schottky contacts on our samples. The annealing studies further revealed hole traps at, 0.15 ± 0.02, 0.23 ± 0.01, 0.38 ± 0.01 and 0.59 ± 0.01 eV each above the valence band. After all the defects were annealed out, the sample was irradiated with 2 MeV protons at room temperature and two primary hole traps, 0.15 eV and 0.32 eV were observed. The complete defect structure was then obtained by studying the defect annealing behaviour as well as the depth profiles of the defects.

Field dependence of the E1′ and M3′ electron traps in inductively coupled Ar plasma treated n-Gallium Arsenide

Inductively coupled Ar plasma etching of n-type (Si doped) Gallium Arsenide (GaAs) introduces several electron traps, Ec – 0.04 eV (labelled E1 0 ), Ec – 0.19 eV, Ec – 0.31 eV, Ec – 0.53 eV, and Ec – 0.61 eV (behaving like the well documented M3 and labelled M3 0 in this study), of which the metastable defects Ec –0 .04 eV (E1 0 ), and Ec – 0.07 eV are novel. Furthermore, E1 0 and M3 0 exhibit strong field enhanced carrier emission. Double-correlation deep level transient spectroscopy was used to investigate the field dependent emission behaviour of these two defects. It is shown that for both traps, the observed enhanced emission is due to phonon assisted tunnelling. The latter observation is contrary to the literature reports suggesting that enhanced carrier emission for M3 occurs via the Poole-Frenkel mechanism. V C 2012 American Institute of Physics.