Growth of SiGe by D-UHV/CVD at Low Temperature

The temperature is a key factor for the quality of the SiGe alloy grown by D-UHV/CVD. In conventional conditions,the lowest temperature for SiGe growth is about 550℃. Generally, the pressure of the growth chamber is about 10~(-5) Pa when liquid nitrogen is introduced into the wall of the growth chamber with the flux of 6sccm of the disilane gas. We have succeeded in depositing SiGe films at much lower temperature using a novel method. It is about 10.2 Pa without liquid nitrogen, about 3 magnitudes higher than the traditional method,leading to much faster deposition rate. Without liquid nitrogen,the SiGe film and SiGe/Si superlattice are grown at 485℃. The DCXRD curves and TEM image show that the quality of the film is good. The experiments show that this method is efficient to deposit SiGe at low temperature.

Growth of 0.55eV-GaInAsSb Quaternary Alloy Films for a Thermophotovoltaic Device by Liquid Phase Epitaxy

Lattice matched Ga_(1-x)In_xAs_ySb_(1-y) quaternary alloy films for thermophotovoltaic cells were successfully grown on n-type GaSb substrates by liquid phase epitaxy. Mirror-like surfaces for the epitaxial layers were achieved and evaluated by atomic force microscopy. The composition of the Ga_(1-x)In_xAs_ySb_(1-y) layer was characterized by energy dispersive X-ray analysis with the result that x = 0.2, y = 0.17. The absorption edges of the Ga_(1-x)In_xAs_ySb_(1-y) films were determined to be 2. 256μm at room temperature by Fourier transform infrared transmission spectrum analysis, corresponding to an energy gap of 0.55eV. Hall measurements show that the highest obtained electron mobility in the undoped p-type samples is 512cm2~/(V·s) and the carrier density is 6. 1×10~(16)cm~(-3) at room temperature. Finally, GaInAsSb based thermophotovoltaic cells in different structures with quantum efficiency values of around 60% were fabricated and the spectrum response characteristics of the cells are discussed.

Heteroepitaxial Growth of 3C-SiC Films on Maskless Patterned Silicon Substrates

Heteroepitaxial growth of 3C-SiC on patterned Si substrates by low pressure chemical vapor deposition (LPCVD) has been investigated to improve the crystal quality of 3C-SiC films. Si substrates were patterned with parallel lines, 1 to 10μm wide and spaced 1 to 10μm apart, which was carried out by photolithography and reactive ion etching. Growth behavior on the patterned substrates was systematically studied by scanning electron microscopy (SEM). An air gap structure and a spherical shape were formed on the patterned Si substrates with different dimensions. The air gap formed after coalescence reduced the stress in the 3C-SiC films, solving the wafer warp and making it possible to grow thicker films. XRD patterns indicated that the films grown on the maskless patterned Si substrates were mainly composed of crystal planes with (111) orientation.

Low-Temperature Growth of ZnO Films on GaAs by Metal Organic Chemical Vapor Deposition

ZnO thin films were grown on GaAs （001） substrates by metal-organic chemical vapor deposition （MOCVD） at low temperatures ranging from 100 to 400℃. DEZn and 1-12 O were used as the zinc precursor and oxygen precursor, respectively. The effects of the growth temperatures on the growth characteristics and optical properties of ZnO films were investigated. The X-ray diffraction measurement （XRD） results indicated that all the thin films were grown with highly c- axis orientation. The surface morphologies and crystal properties of the films were critically dependent on the growth temperatures. Although there was no evidence of epitaxial growth, the scanning electron microscopy （SEM） image of ZnO film grown at 400℃ revealed the presence of ZnO microcrystallines with closed packed hexagon structure. The photoluminescence spectrum at room temperature showed only bright band-edge （3. 33eV） emissions with little or no deep-level e- mission related to defects.

Growth of near planar Si0.5Ge0.5 epitaxial layers directly on Si substrate by UHV/CVD at 500℃

The relationship between Ge content of Si1-xGex layers and growth conditions was investigated via UHV/CVD system at relative low temperature of 500℃. Si1-xGex layers were in a metastable state in this case. 10-period strained 3.0 nm- Si0.5Ge0.5/3.4 nm- Si multi quantum wells were obtained directly on Si substrate. Raman Measurement, high resolution electron microscopy and photoluminescence were used to characterize the structural and optical properties. It is found that such relative thick Si0.5Ge0.5/Si multi quantum wells are still near planar and free of dislocations, that makes it exploit applications to electrical and optical devices.

Growth of Space Ordered on GaAs（100） Vicinal 1.3μm InAs Quantum Dots Substrates by MOCVD

Space ordered 1.3μm self-assembled InAs QDs are grown on GaAs（100） vicinal substrates by MOCVD. Photoluminescence measurements show that the dots on vicinal substrates have a much higher PL intensity and a narrower FWHM than those of dots on exact substrates, which indicates better material quality. To obtain 1.3μm emissions of InAs QDs, the role of the so called InGaAs strain cap layer （SCL） and the strain buffer layer （SBL） in the strain relaxation process in quantum dots is studied. While the use of SBL results only in a small change of emission wavelength,SCL can extend the QD＇s emission over 1.3μm due to the effective strain reducing effect of SCL.

Homoepitaxial Growth of 4H-SiC and Ti/4H-SiC SBDs

Homoepitaxial growth of4H-SiC on off-oriented Si-face （0001） 4H-SiC substrates was performed at 1500℃ by using the step controlled Epitaxy. Ti/4H-SiC Schottky barrier diodes （SBDs） with blocking voltage over lkV have been made on an undoped epilayer with 32μm in thick and 2-5 × 10^15 cm^-3 in carrier density. The diode rectification ratio of forward to reverse （defined at ± 1V） is over 107 at room temperature and over 10^2 at 538K. Their electrical characteristics were studied by the current-voltage measurements in the temperature range from 20 to 265 ℃. The ideality factor and Schottky barrier height obtained at room temperature are 1.33 and 0. 905eV, respectively. The SBDs have on-state current density of 150A/cm^2 at a forward voltage drop of about 2.0V. The specific on-resistance for the rectifier is found to be as 7.9mΩ · cm^2 and its variation with temperature is T^2.0.

LPCVD Growth of 3C-SiC on Si Mesas and SiO2/Si Substrates for MEMS Applications

This paper presents the development of LPCVD growth of 3C-SiC thin films grown on Si mesas and thermally oxidized SiO2 masks over Si with an area of 150 × 100μm^2 and SiO2/Si substrates. The growth has been performed via chemical vapor deposition using SiH4 and C2H4 precursor gases with carrier gas of H2. 3C-SiC films on these substrates were characterized by optical microscopy, X-ray diffraction （ XRD ）, X-ray photoelectron spectroscopy （ XPS ）, scanning electron microscopy （SEM） and room temperature Hall effect measurements. It is shown that there were no voids at the interface between 3C-SiC and SiO2.

MBE Growth of High Electron Mobility InP Epilayers

The molecular beam epitaxial growth of high quality epilayers on （100） InP substrate using a valve phosphorous cracker cell over a wide range of P/In BEP ratio （2.0-7.0） and growth rate （0.437 and 0. 791μm/h）. Experimental results show that electrical properties exhibit a pronounced dependence on growth parameters,which are growth rate, P/In BEP ratio, cracker zone temperature, and growth temperature. The parameters have been optimized carefully via the results of Hall measurements. For a typical sample, 77K electron mobility of 4.57 × 10^4 cm^2/（V · s） and electron concentration of 1.55×10^15 cm^-3 have been achieved with an epilayer thickness of 2.35μm at a growth temperature of 370℃ by using a cracking zone temperature of 850℃.

Single Layer Growth of Strained Epitaxy at Low Temperature

Contacting mode atomic force microscopy (AFM) is used to measure the In0.asGao.65As/GaAs epilayer grown at low temperature (460°C). Unlike the normal layer-by-layer growth (FvdM mode) or self-organized islands growth (SK mode) ,samples grown under 460 C are found to be large islands with atomic thick terraces. AFM measurements reveale near one monolayer high steps. This kind of growth is good between FvdM and SK growth modes and can be used to understand the evolution of strained epitaxy from FvdM to SK mode.

Spotsize Converter Integrated DFB Laser Diode Using Selective Area Growth of MOCVD

The characteristics of thickness enhancement factor and bandgap wavelength of selectively grown In-GaAsP are investigated. A high thickness enhancement factor of 2.9 is obtained. Spotsize converter integrated DFB lasers are fabricated by using the technique of SAG. The threshold current is as low as 10.8mA. The output power is 10m W at 60mA without coating and the SMSR is 35.8dB. The vertical far field angle (FWHM) is decreased from 34 °to 9 °. The tolerance of 1dBm misalignment is 3.4μm vertically.

Growth of Cubic GaN by MOCVD at High Temperature

High quality cubic GaN (c-GaN) is grown by metalorganic vapor deposition (MOCVD) at an increased growth temperature of 900 ℃, with the growth rate of 1.6 μm/h. The full width at half maximum (FWHM) of room temperature photoluminescence (PL) for the high temperature grown GaN film is 48meV. It is smaller than that of the sample grown at 830 ℃. In X-ray diffraction (XRD) measurement, the high temperature grown GaN shows a (002) peak at 20° with a FWHM of 21'. It can be concluded that, although c-GaN is of metastable phase, high growth temperature is still beneficial to the improvement in its crystal quality. The relationship between the growth rate and growth temperature is also discussed.

Growth of SiGe Films by Cold-wall UHV/CVD Using GeH_4 and Si_2H_6

国家自然科学基金,国家863计划

Growth of GaN on magnesium aluminate substrate by LP-MOVPE

于2010-11-23批量导入