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We have investigated the effect of native oxide on the epitaxial SiGe from deposited amorphous Ge on Si. Instead of epitaxial growth by molecular beam epitaxy or ultrahigh-vacuum chemical vapor deposition, the SiGe layer is formed by this simple process followed by an annealing step. As observed by transmission electron microscopy, the suppression of native oxide plays an important role to achieve epitaxial SiGe. The SiGe quality degrades with increasing native oxide thickness and becomes polycrystalline with a ∼20 A interfacial native oxide. On the other hand, single crystalline SiGe can be routinely formed from a HF-vapor treated Si surface.

We have designed a simple‐hot wall low pressure chemical vapor deposition (LPCVD) system to grow high quality epitaxial Si films from 550 to 900 °C. The epitaxial film has been examined by scan electron microscopy for surface morphology, and by x‐ray diffraction and cross‐sectional transmission electron microscopy for crystallinity. Its quality has been found comparable to that of the substrate. Reduction of moisture and oxygen in the ambient is critical to the success of the growth at low temperatures. A combination of a leak‐tight LPCVD reactor, a high flow rate of 61/min of H2 purge, and a pre‐bake at high temperature of 950 °C has been used to achieve the reduction of moisture and oxygen. Degraded films form with increasing full width at half maximum of x‐ray diffraction peak when a pre‐bake at lower temperature is used.

We have studied the growth of InGaAs/GaAs multiple quantum wells (MQWs) on (111)A GaAs. Uniform thickness of (111)A quantum wells is observed by the cross‐sectional transmission electron microscopy (TEM). Growth induced long‐range In‐ and Ga‐rich InxGa1−xAs/InyGa1−yAs superlattice in (111)A is also observed by cross‐sectional TEM in the ternary InGaAs wells. In contrast, none of the above superstructure was observed by TEM on a side‐by‐side grown (100) oriented substrate. However, the photoluminescence (PL) linewidth is broadened by such compositional modulation. Low‐temperature (15 K) photoluminescence showed a broad PL linewidth of 27.5 meV for In0.16Ga0.84As/GaAs MQWs grown on (111)A substrates at 520 °C. A decreased PL linewidth of 15.7 meV and a reduced compositional modulation in InGaAs wells can be achieved at a higher growth temperature of 560 °C.

Cross‐sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 °C. A columnar polycrystalline GaAs is observed for samples grown at 160 °C while it appears amorphous for samples grown at temperatures below 120 °C. The successful growth of amorphous (Ga,As) at 70 °C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as‐grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (∼500 A in size) whose grain boundaries prov...