Si Double Heterostructure Research Articles

Epitaxial orientation of Mg2Si(110) thin film on Si(111) substrate

Epitaxial Mg2Si(110) thin film has been obtained on Si(111) substrate by thermally enhanced solid-phase reaction of epitaxial Mg film with underlying Si substrate. An epitaxial orientation relationship of Si(111)∥Mg2Si(110) and Si⟨11¯0⟩∥Mg2Si⟨11¯0⟩ has been revealed by transmission electron microscopy. The formation of the unusual epitaxial orientation relationship is attributed to the strain relaxation of Mg2Si film in a MgO∕Mg2Si∕Si double heterostructure.

Growth of Si∕β-FeSi2∕Si double-heterostructures on Si(111) substrates by molecular-beam epitaxy and photoluminescence using time-resolved measurements

Highly [110]∕[101]-oriented semiconducting iron disilicide β-FeSi2 continuous films were grown on Si(111) by molecular-beam epitaxy (MBE) using a β-FeSi2 epitaxial template formed by reactive deposition epitaxy. The optimum MBE growth temperature was determined to be about 750°C. At this temperature, the full width at half maximum β-FeSi2(220)∕(202) x-ray diffraction peak was at a minimum. Subsequent MBE overgrowth of an undoped Si layer was performed on the β-FeSi2 at 500°C, resulting in the Si∕β-FeSi2∕Si double heterostructure. After annealing the wafers at 800°C in Ar for 14h, 1.55μm photoluminescence (PL) was obtained at low temperatures. Time-resolved PL measurements elucidated that the luminescence originated from two sources, one with a short decay time (τ∼10ns) and the other with a long decay time (τ∼100ns). The short decay time was thought to be due to carrier recombination in β-FeSi2, whereas the long decay time was due probably to a dislocation-related D1 line in Si.

Type and charge states of point defects in heavily As- and B-doped silicon

In order to determine the type and charge states of dominant point defects in As- and B-doped silicon, self-diffusion in doped natural Si/ 30Si/natural Si double-heterostructures has been investigated under oxidizing ambient. Enhanced self-diffusion is observed in B-doped Si, while retarded self-diffusion is observed in As-doped Si. These results indicate that single-charged Si self-interstitals (I + donors) are dominant in B-doped Si, while excess single-charged vacancies (V − acceptors) exist in As-doped Si.

Room temperature photocurrent spectroscopy of SiGe/Si p-i-n photodiodes grown by selective epitaxy

We present the photocurrent spectroscopy of Si/sub 1-x/Ge/sub x//Si double heterostructure p-i-n diodes selectively grown by low pressure chemical vapor deposition. The growth onto patterned wafers permits to obtain dislocation-free, fully strained Si/sub 1-x/Ge/sub x/ layers, much above the critical thickness. The band gap energy of Si/sub 1-x/Ge/sub x/ was determined at room temperature using the photocurrent spectra for Ge concentration in the range x=0.12-0.20 and compared to similar data obtained by electroluminescence.

Evaluation of the valence band discontinuity of Si/Si/sub 1-x/Ge/sub x//Si heterostructures by application of admittance spectroscopy to MOS capacitors

In this study, admittance spectroscopy is applied for the first time to MOS capacitors fabricated on Si/Si/sub 1-x/Ge/sub x//Si double-heterostructures, in order to evaluate the valence band discontinuity /spl Delta/E/sub v/ at the Si/Si/sub 1-x/Ge/sub x/ interface. The principle of the measurement is presented and verified by the experimental results. A new feature of admittance spectroscopy applied to MOS capacitors is the ability to select the interface whose barrier is measured, by controlling the gate voltage. This fact is confirmed by the measurement of MOS capacitors, which include a SiGe well with different Ge contents at the front and the back interfaces. It is found from this measurement that, while /spl Delta/E/sub v/ at the back interface of the double-heterostructure is measured under slight depletion conditions for MOS capacitors, /spl Delta/E/sub v/ averaged between the front and the back interfaces is measured under accumulation conditions. The Ge/sub x/ content dependence of the measured /spl Delta/E/sub v/ is found to be in fairly good agreement with the theoretical values.

Low temperature formation of Si/silicide/Si double heterostructures by self-aligned MBE growth

Abstract New formation technique of high quality Si/CoSi 2 /Si double heterostructures and fine patterning of CoSi 2 electrodes were developed using self-aligned and two-step molecular beam epitaxy (MBE). In addition, a permeable base transistor (PBT) was successfully fabricated, which showed a high mutual conductance ( g m ) of 42 mS mm −1 .

Formation of High-Quality Si/CoSi2/Si Double Hetero-Structures by Self-Aligned and Two-Step Molecular Beam Epitaxy

AbstractThe formation and application of Si/CoSi2/Si double heterostructures are comprehensively studied. A high-quality double heterostructure is formed by two-step molecular beam epitaxy of the Si over layer, i.e., low -temperature growth followed by high-temperature growth. The interfaces between CoSi2 and Si observed by cross-sectional transmission microscopy are atomically abrupt and smooth. In addition, a new fine patterning method of CoSi2 films using self-aligned and selective growth is developed. Finally, permeable base transistors (PBT) with high performance (gm=50 mS /mm) are fabricated using these new techniques.