Solid State Phenomena Vols. 131-133

Abstract: High temperature anneal of SOI wafers in oxygen-free atmosphere results in internal buried oxide dissolution and top Si layer etching. Dissolution rate is determined by interstitial oxygen diffusion through the top Si layer and evaporation from the top Si surface in the form of SiO. It has been observed that kinetics of the process follows linear-parabolic law. Simple thermodynamic model is proposed, which explains observed dependences on temperature and top Si layer thickness.

Abstract: The degradation and recovery behavior of device performance on GaAlAs LEDs (Light emitting diodes) irradiated by 2-MeV electrons and 70-MeV protons are investigated. The reverse current increases after irradiation, while the capacitance decreases. The device performance degradation is proportional with fluence. For electron irradiation, fluence rate is also effective for degradation. Low fluence rate shows more large degradation compared to high fluence rate resulting from heat impact in bulk. DLTS measurement reveals the DX center in epitaxial substrate, and this spectrum increases with fluence. The radiation damage of proton is larger than that of electron irradiation, which is caused by the difference of mass and possibility of nuclear collision for the formation of lattice defects. After irradiation, the device performance recovers by thermal annealing.

Abstract: Fast neutron irradiation of germanium has been used to study vacancy reactions and vacancy clustering in germanium as a model system to understand ion implantation and the vacancy reactions which are responsible for the apparently low n-type doping ceiling in implanted germanium. It is found that at low neutron doses (~1011cm-2) the damage produced is very similar to that resulting from electron or gamma irradiation whereas at higher doses (> 1013cm-2) the damage is similar to that resulting from ion implantation as observed in the region near the peak of a doping implant. Electrical measurements including CV profiling, spreading resistance, Deep- Level Transient-Spectroscopy and high resolution Laplace Deep-Level Transient-Spectroscopy have been used in conjunction with positron annihilation and annealing studies. In germanium most radiation and implantation defects are acceptor like and in n-type material the vacancy is negatively charged. In consequence the coulombic repulsion between two vacancies and between vacancies and other radiation-induced defects mitigates against the formation of complexes so that simple defects such as the vacancy donor pair predominate. However in the case of ion implantation and neutron irradiation it is postulated that localized high concentrations of acceptor like defects produce regions of type inversion in which the vacancy is neutral and can combine with itself or with other radiation induced acceptor like defects. In this paper the progression from simple damage to complex damage with increasing neutron dose is examined.

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.

Abstract: The behavior of Sb and In atoms embedded into silicon-on-insulator structure (SOI) near the bonding interface was investigated as a function of annealing temperature. Two kinds of the ionimplanted SOI structures were prepared. First kind of the structures contained the buried SiO2 layer implanted with In+ and Sb+ ions near the top Si/SiO2 interface. In second kind, the ion-implanted regions were placed on each side of the bonding interface: Sb+ ions were implanted into Si film; In+ ions were implanted into SiO2 layer. Rutherford backscattering spectrometry (RBS) and crosssectional high-resolution electron microscopy (XTEM) were employed to study the properties of the prepared structures. The formation of InSb nanocrystals was observed within the SiO2 bulk from first kind of the SOI structures as annealing temperature increased to 1100o C. In the case of the double side implanted SOI structures, an increase in annealing temperature to 1100o C was accompanied by the up-hill diffusion of In atoms from the SiO2 bulk toward the bonding interface and by the endotaxial growth of InSb nanocrystals on the top Si/SiO2 interface. It was concluded from the experimental results that Sb atoms were the nucleation centers of InSb phase.

Abstract: The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator (SOI) structures are studied. It is shown that no germanium nanocrystals are formed in the buried SiO2 layer of the SOI structure as a result of annealing at the temperature of 1100° C. The implanted Ge atoms segregate at the Si/SiO2 bonding interface. In this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. It is found that the slope of the drain–gate characteristics of the back metal-oxide-semiconductor (MOS) transistors, prepared in the Ge+ ion implanted structures, increases. This effect is attributed to the grown hole mobility due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface.

Abstract: Results are presented of a comparative study of carrier lifetime in silicon and germanium. The impact of surface quality and passivation, of dopant type and concentration and of metallic impurities is studied using microwave probed free carrier absorption transient techniques.

Abstract: Minority carrier diffusion lengths were measured for the set of n- and p-type silicon samples with NiSi2 precipitates of different electronic structure. We found that the type of precipitate electronic states in the upper part of band gap had no influence on the recombination activity of NiSi2 precipitates. Minority carrier diffusion length L was found to be related to the precipitate density N and L ~ 2 × N -1/3 for n-type Si samples and L ~ 1 × N -1/3 for p-Si samples. Hydrogenation of the p-type Si sample with nanoscale nickel silicide precipitates resulted in an increase of the L value up to a factor of 3, while in n-Si L remained practicaly the same. The only hole emission in the samples of both conductivity types was detected in MCTS measurements and the cross section for the hole capture with the electronic states of the precipitaes was estimated to be as large as 10-11 cm-2.

Abstract: An unusual pattern of the Oxidation Induced Stacking Faults (OISF) in the heavily boron-doped silicon is reported. Instead of the commonly reported simple OISF ring, we observe a banded OISF pattern. The pattern reflects the distribution of residual vacancies as it is described by Voronkov and Falster [J. Crystal Growth 204 (1999) 462]. We show that the oxygen precipitates in the L- and H- bands grow to an abnormally large size during the crystal growth and which serve as the OISF nuclei during subsequent wafer oxidation. It is concluded that a combination of the high boron, oxygen and vacancy concentration is responsible for the enhanced oxygen precipitation during the crystal growth.