Solid State Phenomena Vols. 131-133

Abstract: The samples of p- and n-doped Fz Si were deformed in 3-point bending mode in the temperature range 800-950flC. Dislocation related PL (DRL) spectra were measured at temperature in the range 4.2 – 200K. Several features of DRL turned out to be sensitive to donor level doping. First, the low energy components of D1/D2 bands disappear at middle and high doping level. Second, the intensity of D1 band showed much more dependence on the donor doping level than other DRL bands and almost disappeared at the concentration of donors around 1017cm-3. Finally, it has been found that the temperature variation of the D1/D2 line positions depend on the donor doping level. Namely, at the donor concentration higher than 1015cm-3 the D1/D2 bands demonstrate the blue shift when the sample temperature goes up from 4K. At higher temperature the band positions more or less follow the temperature behavior of the band gap. The effect does not depend on chemical nature of donor except a value of ionization energy. No such behavior has been observed for different levels of acceptor doping. Taking into account that the ionization of shallow donors happens in the temperature range of above 30K, the effect of blue shift has been attributed to the influence of free electrons released from donors.

Abstract: Terahertz-range photoluminescence from silicon-germanium crystals and superlattices doped by phosphor has been studied under optical excitation by radiation from a mid-infrared CO2 laser at low temperature. SiGe crystals with a Ge content between 0.9 and 6.5 %, doped by phosphor with a concentration optimal for silicon laser operation, do not exhibit terahertz gain. On the contrary, terahertz-range gain of ~ 2.3 - 3.2 cm-1 has been observed for donor-related optical transitions in Si/SiGe strained superlattices at pump intensities above 100 kW/cm2.

Abstract: The crystallographic structure of semiconductor - insulator - semiconductor (SIS) structures consisting of a Si(111) substrate, Pr2O3 and Y2O3 insulating high-k materials, and Si cap layer was characterized by a combination of X-ray pole figure measurement and conventional X-ray diffraction. Oxide and Si cap layer were grown by molecular beam epitaxy and have the same 111 lattice orientation as the substrate. It is shown that the oxide layers grow in a type B stacking orientation only, while the epi-layer exhibits exclusively the same type A orientation as the substrate. A small fraction of the epi-Si lattice was identified with 511 netplanes parallel to the surface. TEM investigations identify these areas as structural defects between Si grains of differing stacking sequence.

Abstract: The ZnO/n+-Si heterojunction has been fabricated via depositing nominally undoped ZnO film by reactive sputtering on a heavily arsenic-doped (n+) silicon substrate. The sputtered ZnO film was n-type in conductivity with an electron concentration of 1.0×1018 cm-3. The current-voltage characteristics indicate that the ZnO/n+-Si heterojunction does not possess rectifying function. Under the forward bias with the negative voltage applied on the n+-Si substrate, the heterojunction emits ultraviolet and broad visible lights characteristics of near-band-edge and defect-related emissions of ZnO, respectively. The EL mechanism has been tentatively explained in terms of the energy-band diagram.

Abstract: The local cathodoluminescence is used to study the point defects and their depth distribution in silicon oxide and silicon. The defects formed by two-coordinate silicon (Si=Si), oxygen vacancies (Si-Si, Si-Si-Si), non-bridgen oxygen (-O.), amorphous silicon and silicon nanoclusters have characteristic emission bands. High sensibility of cathodoluminescence method permits to study natural silicon oxide film, thin silicon oxide and silicon layers near the interface. In this paper an influence of the silicon type on the properties of SiO2/Si interface is discussed. It is shown that the quality of SiO2/Si interface depends not only on the technology process but on the silicon type and activator concentration. A high boron content in silicon leads to an increase of point defects concentration in silicon oxide and sometimes to an appearance of Si nanoclusters near the interface in the layer with 10-20 nm thickness. The concentration of intrinsic defects near the silicon oxide – n-silicon interface depends also on phosphorous concentration. But in this case low concentration of activator leads to a presence of high content of intrinsic defects in the first monolayers of silicon oxide and to a dramatical decrease of a content of these defects in films with thickness of more that 10 nm. On the contrary, the high concentration of activators leads to low content of intrinsic defects near the interface and a rise of its content in the film with thickness more that 10 nm.