Solid State Phenomena Vols. 178-179

Abstract: The changes of the positron lifetime and loss/recovery of shallow donor states in n-FZ-Si:P material irradiated at the room temperature with 15 MeV protons have been investigated in the course of isochronal annealing. Thermally stable point radiation defects which begin to anneal at ~ 300 C° – 340 C° have been revealed; they manifest themselves as deep donors. It is argued that these defects involve, at least, more than one vacancy and the impurity atom (s) of phosphorus.

Abstract: The microscopic nature of hydrogen decorated defect complexes created by proton implantation in silicon and subsequental annealing is not well understood yet. We investigated the defects and donator complexes using positron lifetime measurements and Doppler-broadening spectroscopy. In particular, the influence of variations in implantation dose, annealing temperature and annealing time on crystal defects were examined in Czochralski and in float zone silicon samples. Due to well known positron lifetimes in silicon an identification of certain defect complexes was possible.

Abstract: We report on study of oxygen precipitates grown in Czochralski silicon wafers investigated by x-ray diffraction in Bragg reflection geometry and Laue transmission geometry. The analysis of diffraction curves in Laue geometry was done using Takagi equations and statistical dynamical theory of diffraction. These techniques allow us to determine as the radius of defect area as the defect concentrations from measurement in Laue geometry. These results obtained on silicon wafers exposed to two-step and three-step treatments were compared with other experimental techniques including transmission electron microscopy and infrared absorption spectroscopy, while only the largest precipitates are detected by other techniques. The results of all methods are in good agreement.

Abstract: Elaborated characterization tools play an important role for the further improvement of solar material and the development of solar cells. Besides the huge variety of highly advanced methods mainly based on optical and electrical measurements, the direct measurement of surface currents by the detection of their induced magnetic fields has gained less attention. The novel method current-analysis-by-inductive-coils (CAIC) based on an inductive coil detector and is reviewed and compared with already established methods, which are light-beam-induced-current (LBIC) and dark-lock-in-thermography (LIT). The detector reveals complementary information at high resolution. The LIT measurements depicted shunting defects in forward and reverse current. Because of the high spatial resolution of the CAIC measurement technique it was determinable that in some cases the positions of current sinks in the CAIC maps are not corresponding with the microstructure. The analyses of the superpositions reveals macroscopic precipitates like SiC and Si₃N₄ filaments and clusters as an origin of some of the shunts.

Abstract: Luminescent and structural properties of silicon layers with dislocation-related luminescence have been studied. Silicon ions (100 keV) were implanted into n-FZ-Si wafers at a dose exceeding the amorphization threshold by two orders of magnitude. The implantation was not followed by amorphization of the implanted layers. A post-implantation annealing resulted in the formation of luminescence centers and extended structural defects. Some fundamental aspects and specific features in the properties of dislocation-related luminescence lines and extended structural defects were revealed in relation to the annealing conditions.

Abstract: Results are presented of a comparative study of diodes processed on n-type Cz grown Si substrates without and with Ge doping concentration of about 10¹⁹ cm^-3 and 10²⁰ cm^-3. In order to investigate thermal donor formation, isothermal annealing at 450°C for 0.5 – 5 h was carried out. As processed diodes were also irradiated with 2 MeV electrons with fluences in the range between 10¹⁴ and 10¹⁷ e/cm² to investigate the Ge doping influence on irradiation induced defect formation. Diodes after thermal and radiation treatments have been investigated by combining different techniques.

Abstract: The measurement of Pendellösungs oscillations was used to observe the time dependent nucleation of oxygen in a Czochralski grown single crystal at 750°C. It is shown, that the theoretical approach of the statistical dynamical theory describes the data well. Within the framework of this theory it is possible to determine the static Debye-Waller-factor as a function of the annealing time by evaluating the mean value of the Bragg intensity and the period length. The temperature influence on the Pendellösungs distance was corrected for by measurement of a Float-zone sample at the same temperature.

Abstract: A defocused Laue diffractometer setup operating with the white beam of a high energy X-ray tube has been used for a topographic visualization of structural defects in semiconductor wafers. The laboratory white beam X-ray topograph of a Czochralski Si wafer with oxygen precipitates grown in an annealing process is compared to a μPCD image. Further, the dislocation network in a VGF GaAs wafer is studied under thermal annealing up to 1140°C and the in-situ capability of the setup is demonstrated.

Abstract: Deep-level defects in 4H-SiC Schottky diodes were studied using deep level transient spectroscopy (DLTS). The epitaxial layers, doped with N and grown on standard n+4H-SiC substrates were exposed to aluminium ion implantation process under the Schottky contact and of junction termination extension (JTE). The studies performed within 80-400 K temperature range revealed five deep electron traps, with a dominant double peak at around room temperature related to the Z1/Z2 defect. The thorough analysis of the DLTS-line shape and DLTS-line behaviour on DLTS measurement conditions made possible to distinguish and identify all the observed deep levels.

Abstract: By introducing radiation damage and hydrogen and successively annealing with low thermal budgets, hydrogen-related donors are created in oxygen-lean silicon. Hydrogen-related donor profiles are induced in float-zone silicon by implanting hydrogen and/or helium and successive annealing with or without additional hydrogen introduction by a hydrogen plasma. The efficiency of the conversion of the radiation-induced damage into the hydrogen-related donors differs in dependence of the method of damage and hydrogen introduction. In proton implanted samples, the ultimate introduction rate of the donors is significantly lower than it is in helium and hydrogen co-implanted samples. Furthermore, the depth distribution of the hydrogen-related donors shows a deviance from the simulated distribution of the radiation damage induced by proton implantation not seen in case of helium-induced damage. The change in doping efficiency is discussed in respect to the hydrogen content in the different experiments.