Papers by Keyword: Hydrogen Implantation

Abstract: In this study, we investigated the generation of trap centers through hydrogen implantation to understand its role in the suppression of forward bias degradation in 4H-silicon carbide (4H-SiC) bonded substrates. During the production of bonded substrates, hydrogen implantation is used for layer splitting. Transmission electron microscopy (TEM) observations revealed that the basal plane dislocation (BPD) in the bonded substrate did not extend into the Shockley-type stacking fault (SSF) and remained stable in the transferred layer below the epitaxial interface even under high forward current stress. Additionally, carrier lifetime, measured using microwave photoconductivity decay (μ-PCD), was considerably reduced by hydrogen implantation. Annealing at 1700°C reduced the implanted hydrogen to levels below the detection limit of secondary ion mass spectrometry (SIMS), yet the carrier lifetime remained short. Deep level transient spectroscopy (DLTS) revealed that, after annealing at 1700°C following hydrogen implantation, the concentration of the Z_1/2 center increased by more than two orders of magnitude compared to pre-implantation levels. Trap centers, including the Z_1/2 center, are believed to help prevent forward bias degradation in the bonded substrates by inhibiting the expansion of SSFs in the transferred layer.

Abstract: Hydrogen implantation at room temperature into monocrystalline silicon leads to the formation of complex defects and also to the appearance of in-plane compressive stress. During annealing hydrogen atoms and vacancies co-precipitate into platelets lying on two types of habit planes. These platelets play a decisive role in the fracture of the material that can occur during further annealing and which is used for the manufacture of SOI wafers. Thus, their stress assisted nucleation mechanism has to be well understood. Here, we develop a formalism based on the Volmer’s model which allows calculating the variation of the free Gibbs energy of the system following the nucleation of a platelet. In an unstressed crystal, this energy only relies on the habit plane of the platelet. When the system is under stress, this energy also depends on a term coupling this stress and the strain field generated by the platelet. Because those energies control the nucleation rate of the platelets variants, we could calibrate our model using the transmission electron microscopy observations of the platelets occurrences as a function of depth and, thus, as a function of the magnitude of the intrinsic stress and the angles between the stress direction and Burgers vectors of the considered platelets. These experimental distributions allowed us adjusting the parameters describing the Gibbs free energy of platelets.

Abstract: In the present work, defects created by implantation of hydrothermally grown ZnO single crystals of high quality with H⁺ ions were investigated by positron annihilation lifetime (LT) spectroscopy combined with measurements of optical transmittance (OT) and photoluminescence (PL). First, zinc vacancies attached with one hydrogen impurity (V_Zn – 1H) atom were identified in the virgin ZnO single crystal. The ZnO single crystals were then bombarded by H⁺ ions with the energy of 2.5 MeV to the fluence of 10¹⁶ cm^-2. It was found that V_Zn – V_O divacancies were introduced into ZnO by H⁺-implantation. Effects of H⁺-implantation on the optical activity of defects in ZnO lattice are characterised in the light of the present OT and PL data.

Abstract: It is found that shallow hydrogen-related donors are formed in proton-implanted dilute Ge1-хSiх alloys (0 ≤ x ≤ 0.031) as well as in Si-free Ge samples upon heat-treatments in the temperature range 225-300oC. The maximum concentration of the donors is about 1.5×1016 cm-3 for a H+ implantation dose of 1×1015 cm-2. The temperature range of formation of the protonimplantation- induced donors is the same in Ge1-xSix samples with different Si concentration. However, the increase in Si content results in a decrease of the concentration of the hydrogenrelated donors. It is argued that the H-related donors could be complexes of Ge-self-interstitials with hydrogen atoms. The observed decrease in the concentration of the donors with an increase in Si content in the Ge1-xSix samples is associated with interactions of mobile hydrogen atoms with Si impurity atoms. Such interactions reduce the number of implanted hydrogen atoms that can be involved in defect reactions resulting in the formation of H-related shallow donors.