摘要:

A new scheme for selective area molecular beam epitaxial (MBE) growth is proposed which employs a tungsten masking layer depositedinsituwithin the MBE growth chamber. The complimentary etching characteristics of W and the III–V semiconductor in fluorine and chlorine based plasmas, allows for pattern definition in the tungsten mask layer without affecting the GaAs and a preetch of the GaAs exposed through the mask without disturbing the mask. This latter step was performed in an integrally connected plasma facility in the sample introduction vacuum chamber of the MBE system just prior to growth, thus miminizing surface contamination. Liftoff of the W mask and overlying polycrystalline GaAs is achieved using a fluorine based plasma etching step, leaving single‐crystal free‐standing selectively grown structures ∼1000 Å high and 1–5 μm wide with submicron step profiles. The GaAs surface, reexposed after removal of the W, is as smooth as that of the original starting wafer. The regrowth step can be preceeded by a plasma etch‐back of the exposed GaAs to yield selectively regrown planar structures. Finally the process should eventually be able to be performed entirely in vacuum and is extendable to the broad range of other III–V compounds.

ISSN:1071-1023    

DOI:10.1116/1.583132

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

The selective eptiaxy of GaAs multilayer structures through windows in SiO2deposited on (001) oriented semi−insulating GaAs substrates for GaAs coplanar diodes, has been studied. It is shown that excellent flat, smooth, and straight boundaries of windows can be obtained by use of sidewall orientation with [1̄01] or [101]directions. GaAs coplanar diodes were fabricated by this technique. The characteristics of the polycrystalline GaAs grown on SiO2(001)GaAs, SiO2‐(100)Si, and SiO2‐(111)Ge substrates have been examined by TEM, SEM, and x‐ray diffraction. The results obtained show grain size of 1.0 to 3.3 μm can be achieved. The preferred orientation of the grains were [111], [400]and [800] for polycrystalline GaAs SOI on SiO2‐(001)GaAs and [111] for polycrystalline GaAs SOI on SiO2‐(100)Si and SiO2‐(111)Ge.

ISSN:1071-1023    

DOI:10.1116/1.583133

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Widespread interest in the field of epitaxy has stimulated us to perform a first principles atomistic calculations dealing with the energetics of bicrystals. Using a self‐consistent pseudopotential approach we have calculated total energy as a function of growth sequence of a metal on a semiconductor surface. The prototype system we study is the pseudomorphic growth of aluminum on an unreconstructed Ge(001). For Al(001)–Ge(001) in the epitaxial relationship (001) [100]Al∥(001) [110]Ge where the [100]Al axis has been rotated 45° with respect to the Ge[100]a small lattice mismatch might allow coherency. We present the results of total energy calculations starting from submonolayer coverages of Al to multilayer deposition of metal. Of the two possible symmetric sites (bridge and on top) where the overlayer can begin to grow, our calculation favors the bridge site. Upon increasing the overlayer thickness we found a striking change (∼35% increase) in the interplanar distance between the substrate and the overlayer. The absolute value of the interplanar distance increased from about 1.2 to about 1.7–1.8 Å. An important observation we wish to make is that the interplanar distance between two expitaxially grown systems rapidly tends to stabilize at the average interplanar separation of the constituents. Even though our calculations are for a specific system, we suggest that this might be more generally applicable. An experimental corroboration of this fact should be very valuable. We also present results for the unsupported aluminum film and show that its lattice constant is contracted by about 10% as compared to the bulk value. From this we are able to calculate a realistic value for the elastic energy contribution to the total energy. Some important implications of the thin film effect for the structural properties of the overgrowth are briefly discussed.

ISSN:1071-1023    

DOI:10.1116/1.583134

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

The effects of varying As4/Ga flux ratior, substrate temperature and growth rate on the deviation from stoichiometry in GaAs grown by MBE have been investigated. The deviation from stoichiometry was directly measured by detecting intensity variation of a weak quasiforbidden (200) reflection of x rays. Using this new method, we obtained the following results: in the regions ofr2.0, higher densities were detected in the As lattice plane. The behavior forr<1.0 is contrary to the expectation of decrease of As. A possible explanation for this higher reflection inr<1.0 is that some Ga atoms may exist at interstitial site in the As lattice plane. It is also seen that densities of atoms in the As lattice plane decrease with increasing substrate temperature. In correspondence with the results that the growth condition with flux ratior=1.4 minimizes the deviation from stoichiometry, it is found that GaAs films grown under the conditionr=1.4 show the highest quality of the electrical and optical properties.

ISSN:1071-1023    

DOI:10.1116/1.583135

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Ga adsorption on a GaAs(001)c(2×8) surface prepared by MBE leads to cluster growth at room temperature. This has been observed directly from scanning electron microscopy (SEM) as well as in UV photoelectron spectra (UPS). Schottky diodes prepared from pure Ga metal show a large barrier height (φb≊1 eV). By depositing a thick Al layer on top of such a discontinous Ga film the properties of the bare areas will be characteristic for the Al–GaAs junction (φb=0.75 eV). The resulting metal semiconductor structure can be described with two parallel, ‘‘intermixed’’ diodes (Ga–GaAs and Al–GaAs) with varying relative areas depending on the amount of deposited Ga. The effective barrier height of this structure may consequently be tuned between 0.75 and 1 eV by controlling the Ga coverage on the GaAs, still retaining Al as the top metal for bonding of the device. Results are shown where the barrier has been increased from 0.75 up to 0.87 eV by a Ga surface coverage ranging from 0% to 50%.

ISSN:1071-1023    

DOI:10.1116/1.583137

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

Mn, Ag, and Ag–Mn alloys have been deposited on 001 Ru in an MBE system for the study of the epitaxy of the first few layers when the lattice constants have large mismatches. A new phase of Mn metal is reported. XPS studies of the splitting of the 3speak of Mn is essentially the same in various metallic environments. If this splitting reflects the 3d–3sexchange interactions, it appears that Mn metal has 5 μβ per atom on the time scale of XPS measurements.

ISSN:1071-1023    

DOI:10.1116/1.583139

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.583141

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

It was found that a thick AlGaAs layer grown on a GaAs–AlGaAs superlattice buffer layer does not affect the optical quality of single quantum well structure successibly grown on the AlGaAs layer; that is, background impurities such as carbon and oxygen, which would come from residual gases, do not accumulate on the AlGaAs surface during molecular beam epitaxy (MBE) growth. Extremely high‐quality GaAs–AlGaAs GRIN‐SCH lasers were obtained by introducing a superlattice buffer layer. The minimum threshold current density of 175 A/cm2was achieved for a broad‐area Fabry–Perot laser with a cavity length of 450 μm at room temperature. This is the lowest threshold current density of semiconductor lasers with a similar cavity length.

ISSN:1071-1023    

DOI:10.1116/1.583096

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

摘要:

There is widespread interest in the use of the quantum size effect to modify the operating wavelength of semiconductor lasers, particularly in the AlGaAs/GaAs system where there is the possibility of producing short wavelength devices suitable for optical information systems. High quality current injection quantum well lasers grown by molecular beam epitaxy (MBE) have been reported with well widths as thin as 60 Å producing emission down to about 820 nm. Further reductions in wavelength have only been achieved by the addition of Al to relatively wide wells in which the wavelength shortening due to the quantum size effect is small. In this paper we report on the growth and characteristics of AlGaAs/GaAs multiple quantum well (MQW) injection lasers with thin (≤55 Å) GaAs wells utilizing the quantum size effect alone to obtain emission in the visible region of the spectrum. Growth of these multiple layer structures was carried out in a laboratory designed MBE system with rapid automatic beam shuttering in order to obtain abrupt interfaces and good periodicity. High speed substrate rotation was used to ensure uniformity across the wafer. Accurate determination of well widths is essential for meaningful comparisons between calculated and measured wavelengths, especially when well widths are reduced to a few monolayers. The well widths were determined both from growth rate, calibrated by RHEED oscillations, and by electrochemical profiling of the cladding layers. The structures were processed into oxide stripe lasers to study 300 K emission wavelengths and threshold currents as a function of well width. Laser operation at 300 K has been obtained in all devices, and a device with 13 Å wells gave the shortest wavelength (704 nm) reported for an MQW injection device with GaAs wells. The 300 K emission spectra were compared with both the calculatedn=1(e‐hh) transition for each device and the wavelength of this transition obtained directly by photovoltage spectra on some devices. We have found that the lasing wavelength differs from both the calculated and measuredn=1(e‐hh) transition wavelengths by about 20 nm over the whole range of well widths studied. A strong dependence of threshold currents on number of wells has been observed.

ISSN:1071-1023    

DOI:10.1116/1.583097

出版商:American Vacuum Society    

年代:1985

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.583098

出版商:American Vacuum Society    

年代:1985

数据来源: AIP