MBE Equipment Research Articles

Unleashing the potential of molecular beam epitaxy grown AlGaN-based ultraviolet-spectrum nanowires devices

We acknowledge the financial support from the King Abdulaziz City for Science and Technology (KACST) under Grant No. KACST TIC R2-FP-008. This work was partially supported by the King Abdullah University of Science and Technology (KAUST) baseline funding No. BAS/1/1614-01-01 and MBE equipment funding No. C/M-20000-12-001-77.

Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

Design challenges for matrix assisted pulsed laser evaporation and infrared resonant laser evaporation equipment

Oxford Instruments Plasma Technology gets VG Semicon

After recent speculation, Oxford Instruments Plasma Technology, a wholly owned subsidiary of Oxford Instruments plc, comfirms it has acquired the assets of MBE equipment manufacturer Thermo VG Semicon. Visit www.three-fives.com for the latest advanced semiconductor industry news

Crystalline to amorphous phase transition in very low temperature molecular beam epitaxy

For the first time, we use in situ time resolved reflectivity (TRR) measurement to determine the thickness for crystalline–amorphous transition. The use of TRR measurements to study the breakdown of the single crystalline growth and the following deposition of amorphous silicon ( α-Si) is based on the higher refraction index of α-Si at the wavelengths used (950 and 670 nm). An increasing α-film thickness causes cycles of constructive and destructive interference and leads to a time-dependent reflectivity. Final amorphous film thicknesses have been confirmed by ex situ spectroscopic ellipsometry. Samples were prepared by the deposition of electron-beam evaporated Si in an MBE equipment. The temperature, as a function of heater power, was carefully calibrated for highly doped substrates, with a thermocouple mounted into a test substrate. Substrates were kept at constant growth temperatures between 100 and 250 °C. From an Arrhenius-type expression, we can deduce an activation energy of 0.36±0.05 eV. The growth rate dependence was investigated between 0.013 and 0.7 nm s −1 at a constant temperature of 200 °C. Rate dependent data can be fitted by a power law. A variation of the deposition rate by a factor of 100 causes a variation in epi thickness by a factor 5. Similar experiments were also performed on low doped substrates and with non-linear temperature ramp. The obtained substrate temperature depends strongly on doping because of free carrier absorption (differences up to ≈50 °C).

Temperature dependence of the Faraday rotation for CdMnCoTe films

The temperature dependence of magneto-optical property in the visible wavelength region has been studied on four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A large dispersion of Faraday rotation was observed, and the peak of the Faraday rotation was shifted to the higher photon energies with increasing Mn concentration at low temperatures. At 180 K, the value of the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.36 deg/cmG at 630 nm. It is equivalent to the value of −0.36 deg/cmG observed at 77 K for the Cd0.52Mn0.48Te film on quartz glass. At 77 K, the Faraday rotation observed for the Cd0.647Mn0.34Co0.013Te film on quartz glass was −0.49 deg/cmG at 610 nm. The value is approximately two times larger than that of the Cd0.52Mn0.48Te film deposited on the same quartz glass substrate. The origin of the enhancement of Faraday rotation in CdMnCoTe films has been discussed in terms of the magnetic susceptibility χ.

Magneto-optical properties of four-element semimagnetic semiconductor CdMnCoTe films on quartz glass

Magneto-optical properties in the visible wavelength region have been studied with four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A Faraday rotation value of 0.3 deg/cmG in the (Cd 0.647Mn 0.34Co 0.013) 0.5Te 0.5 film has been observed at 570 nm. This is approximately two times larger than the Faraday rotation for (Cd 0.61Mn 0.39) 0.5Te 0.5 film on quartz glass. By using a vibrating-specimen magnetometer, it has been confirmed that the prepared (Cd 0.647Mn 0.34Co 0.013) 0.5Te 0.5 film is paramagnetic.

Performance of a compact ECR source for MBE equipment

A compact electron cyclotron resonance plasma source has been developed for molecular beam epitaxy equipment. Faraday cup and Langmuir probe were used to measure the ion current densities, electron temperatures, ion densities, and plasma potentials. The ion current densities as function of pressure and microwave power have been studied.

Surface diffusion and adatom stoichiometry in GaAs MBE studied by microprobe-RHEED/SEM MBE

The incorporation diffusion lenght of surface migrating adatoms, λ inc, is studied theoretically and experimentally taking GaAs MBE as an example. By using microprobe-RHEED/SEM MBE equipment, it is demonstrated that λ inc depends strongly on the As pressure and takes a value of the order of 1 μm. This behavior is explained by assuming that the Ga flux entering the step exceeds that of As. On the other hand, when the Ga flux entering the step is less than that of As, λ inc decreases to take the value of step separation which is typically of the order of a few tens of nm. It is concluded that the balance of Ga and As fluxes entering the step edge governs the incorporation diffusion length of Ga.

In situ cleaning of Si surfaces by UV/ozone

We describe an attempt to perform the UV/ozone cleaning step for silicon wafers within the ultrahigh vacuum system. By introducing the UV/ozone cleaning into the load lock of the MBE equipment we avoid the contact of the normally ex situ UV/ozone precleaned substrate to air. In addition we gain a further degree of freedom, namely the oxygen partial pressure. The influence of that pressure on removing carbon-containing contaminations and on the properties of the in situ formed thin oxide layer is investigated by X-ray photoelectron spectroscopy (XPS) without breaking the vacuum.

Morphology and Interface chemistry of the Initial Growth of GAN and ALN on α-SIC and Sapphire

ABSTRACTThe morphology and interface chemistry occurring during the initial stages of growth of GaN and A1N layers has been obtained. Films were grown using gas source MBE equipment containing an ECR plasma source to activate molecular nitrogen. The experiments consisted of sequential depositions of about one monolayer thick films and XPS analysis. Evidence for silicon nitride formation on the SiC surface was obtained from the studies of both the Si oxidation states and the substrate peak intensity dependence on film thickness. The growth of GaN on sapphire appeared to occur via the Stranski-Krastanov mode, while the growth on SiC showed characteristics of three-dimensional growth. AlN grew in a layer-by-layer mode on both substrates.

High Speed Integrated Circuit Using Silicon Molecular Beam Epitaxy (Si‐MBE)

Si‐MBE is a low temperature deposition method for epitaxial silicon layers with thickness and doping profile control on a submicron level. The MBE equipment described in detail is designed for high throughput of round wafers (ten 3 in. wafers per day). The apparatus consists of six subsystems, the reliable and simple operation of which has been proved during a 2 yr test period. For the first time we report on fabrication of high performance integrated circuits using Si‐MBE material. Frequency dividers were fabricated using, apart from MBE, a commercial process line. Clock frequencies of up to 2.8 GHz were realized by these dividers with integrated transistors with transit frequencies up to 7 GHz.