Gas source silicon molecular beam epitaxial (Si-MBE) growth is microscopically governed by a disociative adsorption of silicon hydrides, such as Si2H6 source gas molecules on Si surface. The dissociative adsorption generates SiH species on the surface. From this hydride phase, hydrogen desorbs thermaly. The temperature dependence of the growth rate indicated that the hydrogen desorption from the SiH is the rate limiting step. In HBO2 Knudsen cell doping, B adsorbates block the surface migration. Such a blocking effect can be avoided by B2H6 gas dopant, because of the similar incorpration mechanism of B2H6 to that of Si2H6. However, in PH3 gas doping, a crystal quality degradation was observed at a high doping range due to the preferentially high sticking coefficient of PH3 and the resulting surface dangling bond termination. The selective epitaxial growth of a B doped layer using Si2H6 and B2H6 was applied to a novel structured base fabrication for super self-aligned selectively grown base transistor (SSSBT). A successful achievement of the SSSBT fabrication indicates the high potentiality of gas source Si-MBE to the sub-micron size ultra-high speed bipolar large scale integrated (LSI) circuits.

Rapid thermal processing chemical vapor deposition (RTP-CVD) has received considerable attention because of its ability to reduce many of the processing problems associated with thermal exposure in conventional chemical vapor deposition, while still retaining the ability to grow high quality epitaxial layers. In this paper, the principles of the RTP-CVD system are described, followed by results of experiments on in-situ cleaning, undoped Si epitaxy and in-situ doped Si epitaxy, and selective Si deposition using oxide masks. Our results show that RTP-CVD is capable of growing high quality, epitaxial layers with sharp, dopant transition profiles. Selective deposition was achieved without the use of HC1. We also studied the growth and characterization of GexSi1−x films for optical waveguiding.

Single crystal β-SiC films have been fabricated on (100)Si substrates through a thermal reaction between the substrate and carbon atoms sublimed from a high purity graphite source. The substrate temperature during the deposition ranged from 600 to 1100°C. The film properties were analyzed by RHEED and x-ray diffraction measurements. RBS measurements and TEM observations have also been made to investigate the film properties. The single crystal β-SiC films grow at and above 1000°C on (100) substrates. The activation energy is found to be around 1.1 eV for the crystallization process.

Carbonization dynamics of Si surfaces using a hydrocarbon gas molecular beam was investigated. In case of carbonizing atomically clean Si surfaces with C2H2, single crystalline 3C-SiC layers were obtained only In the narrow range of a substrate temperature near 780 °C. Control of surface reaction by a cap of very thin surface oxide layer and gradual increase of substrate temperature during carbonization were found to be effective in forming single crystalline 3C-SiC layers reproducibly.

We have synthesized Si1−yQy layers and strained layer superlattices on Si (100) with C concentrations of up to a few percent using Solid Source Molecular Beam Epitaxy. The presence of C even in small quantities is known to disrupt the epitaxy of Si. We show that under conditions of high Si flux for a given C/Si flux ratio, defect-free epitaxy results. However, exceeding a critical C/Si flux ratio leads to disruption of epitaxy, initially via twinning and subsequently by amorphous growth. Growth temperature also plays a significant role in preventing twinning and islanding. Low growth temperature also suppresses the precipitation of β-SiC and leads to the formation of pseudomorphic Si1−yQy random alloys. The layers are characterized by X-ray diffraction, Secondary Ion Mass spectroscopy, and Transmission Electron Microscopy. We have also studied the thermal stability of strained layer superlattices and find that the layers are stable to about 800°C (for y = 0.003). Between 800°C and 1000°C, the layers relax by interdiffusion. Above 1000°C, silicon carbide precipitation occurs and the carbide layers nucleate and grow at high C content regions of the film.

This paper reports on a tight-binding calculation of the band structures of the Si-GaP superlattice (SL) systems with emphasis on the results of the band gap properties. This calculation finds that the SLs grown onto the [110] or [111] oriented substrate do not produce direct gap materials. On the other hand, some of the [001] oriented SLs become direct gap materials when either an interface (IF) state is created at the P and Si IF, or a confined state in the Si occurs with only Ga and Si atoms forming all the IF.

Epitaxial growth conditions of perovskite type oxide films on Si substrates are theoretically considered from a viewpoint of lattice matching. Then, epitaxial growth of SrTiO3 films and BaTiO3 films on Si (100) substrates has been tried, in which in order to deoxidize the SiO2 layers on the substrates, thin Sr layers are deposited prior to deposition of the oxide films. It has been found from X-ray diffraction, reflection high energy diffraction, and Rutherford backscattering analyses that SrTiO3 films grow epitaxially on Si (100) substrates under the optimum conditions of the Sr layer thickness, deposition temperature, and annealing temperature.

Conventional high temperature, >800°C, CVD processes, utilizing SiH2Ci2 promote selective deposition of c-Si onto c-Si, but not on SiO2 surfaces. We show that low temperature, 300°C remote PECVD, with rf-excited He plasmas, and SiH2Ci2 and H2 injected downstream, also selectively deposits c-Si on c-Si and not SiO2 surfaces. This preliminary study employs in-situ mass spectrometry, MS, to determine the species responsible for selective deposition process reaction pathways. These MS studies suggest that species responsible for film deposition are Si-containing fragments of the SiH2Ci2 molecule, e.g., SiH2Ci, SiCi2H, etc., while the species responsible for inhibiting deposition on the SiO2 surfaces are by-products of the break-up of the SiH2Ci2 molecule in the gas phase, e.g., H-atoms, HCI and H2Ci+ ions.

Dichlorosilanc and germane were used to grow silicon-germanium alloys at temperatures as low as 550°C at atmospheric pressure. Germanium mole fractions as high as 44% were obtained and the layers exhibit smooth surface morphology. Silicon-gcrmanium/silicon multilayers with abrupt hctero-intcrfaccs have been achieved. Cross Section Transmission Electron Microscopy, (XTEM) and High Resolution X-Ray Diffraction, (HRXRD) characterization of the hetero-interface abruptness will be presented. Recent results on two-dimensional (2-D) hole mobility structures grown by this technique will also be reported. Selective growth of silicon-germanium on oxide patterned silicon wafers was also demonstrated. A significant feature of the selective deposition is the lack of faceting at the oxide sidcwall, which has been commonly observed in high temperature silicon growth.

Epitaxial growth and p-type doping in Si and Si1−xGex alloy by the ultra-high vacuum vapour phase epitaxy (UHV-VPE) method using SiH4/GeH4/B2H/H2 mixture is reported. Growth temperatures as low as 610°C were studied for Ge contents between x=0 to 0.25. Secondary Ion Mass Spectroscopy (SIMS) data of boron dopant profiles in si and Si1−xGex structures are presented. Strong luminescence attributed to the strained Si1−xGex alloy is obtained. The bandgap in the alloy layer obtained from our luminescence data is compared with published data. Unambiguous electroluminescence from a Si1−xGex multiple quantum well p-n structure grown by UHV-VPE, supported by the photoluminescence and photoconductivity measurement, is reported for the first time.

Patterned GexSi1−x/Si wells are fabricated for the first time by pulsed laser induced epitaxy technique, employing two different semiconductor processing steps to grow these structures selectively. Two different dimensions of Gt0.12 Si0.55 /Si wells are sucessfully formed, in which one is 3.5 μm wide and 1700Å deep while another is 6 μm wide and 1300Å deep. Transmission electron microscopy combined with energy-dispersive X-ray imaging reveals that the 2-D Ge redistribution profiles are well defined and no significant line or surface defects observed. The 2-D Ge well redistribution behavior, governed by heat and mass transport during laser processing, are also discussed.

We have demonstrated, for the first time, that the epitaxial growth temperature can be lowered by dopant incorporation using rapid thermal processing chemical vapor deposition (RTPCVD). Heavily arsenic-doped epitaxial layers with very abrupt dopant transition profiles and relative uniform carrier distribution have been achieved at 800°C. The defect formation is closely related to dopant concentration; the defect density as a function of carrier concentration shows a sharp transition at about 3×1018 cm−3.

It is shown that visible photoluminescence and electroluminescence can be obtained from porous silicon layers. Room temperature photoluminescence is readily obtained from as-formed high porosity samples. Light emission at wavelengths as short as 560 nm can be observed after further thinning of the silicon pore walls by dissolution in HF under illumination. Silicon walls can also be thinned by an electrochemical oxidation process, this method allowing to use layers of rather low porosities (65%) which thus gives good mechanical properties to the samples. The thinning of the already very small size crystallites of porous silicon leads to quantum size effects which are at the origin of the light emission far above the band gap of silicon. Photoluminescence decay characteristics suggest that a tunnelling effect could be involved in the recombination mechanism of photogenerated charge carriers. Bright electroluminescence during anodic oxidation of porous silicon has been also evidenced. The influence of the porosity, of the layer thickness and of the anodic current density on the integrated electroluminescence intensity are described in detail.