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1.
A study is made of the electrical, optical, and structural properties of Si:Er layers produced by sublimation molecular-beam epitaxy. The Er and O contents in the layers, grown at 400–600°C, were as high as 5×1018 and 4×1019 cm−3, respectively. The electron concentration at 300 K was ∼10% of the total erbium concentration and the electron mobility was as high as 550 cm2/(V·s). Intense photoluminescence at 1.537 μm was observed from all the structures up to 100–140 K. The structure of the optically active centers associated with Er depended on the conditions under which the layers were grown. Fiz. Tekh. Poluprovodn. 33, 156–160 (February 1999)  相似文献   

2.
BxGa1?xAs layers were grown on GaAs substrates using low-pressure metal-organic vapor-phase epitaxy. Triethylboron, trimethylgallium, and arsine were used as boron, gallium, and arsenic sources. Optimum growth conditions were selected. The layers were studied using X-ray diffraction, secondary-ion mass spectrometry (SIMS), and photocurrent spectroscopy (PCS). The SIMS results showed a uniform boron distribution over the layer thickness. According to the PCS data, the BGaAs band gap decreases as the boron concentration increases.  相似文献   

3.
4.
High quality InAs1−xSbx semiconductor films were successfully grown on (100) GaSb single crystal substrates using liquid phase epitaxy technique (LPE). The crystalline structure and lattice mismatch between film and substrate were investigated by high-resolution X-ray diffraction (HRXRD). The surface roughness and the interface morphology of the epitaxial film-on-substrate were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical microscopy. These results show the high-purity InAs1−xSbx epitaxial layers with mirror-like surface and rms ranges from 0.5 to 2 nm, and a sharp interface between substrate and ternary film. The optical properties of the layers were studied by low temperature photoluminescence (PL) spectroscopy. PL spectrum of the ternary film shows one radiative emission peak with narrow full width at half-maximum, which is an evidence of the good crystalline quality of the epilayer. It is worth to mention that the InAsSb films were grown on GaSb substrates for compositions of Sb with x=0.16 without introducing any intermediate composition buffer layer between the GaSb substrate and the film as reported in previous works.  相似文献   

5.
This paper describes studies of InGaAs layers grown by molecular-beam epitaxy on InP (100) substrates at temperatures of 150–480 °C using various arsenic fluxes. It was found that lowering the epitaxy temperature leads to changes in the growth surface, trapping of excess arsenic, and an increased lattice parameter of the epitaxial layer. When these lowtemperature (LT) grown samples are annealed, the lattice parameter relaxes and excess arsenic clusters form in the InGaAs matrix. For samples grown at 150 °C and annealed at 500 °C, the concentration of these clusters was ∼8×1016 cm−3, with an average cluster size of ∼5 nm. Assuming that all the excess arsenic is initially trapped in the form of antisite defects, the magnitude of the LT-grown InGaAs lattice parameter relaxation caused by annealing implies an excess arsenic concentration (N AsN GaN In)/(N As+N Ga+N In)=0.4 at.%. For layers of InGaAs grown at 150 °C, a high concentration of free electrons (∼1×1017 cm−3) is characteristic. Annealing such layers at 500 °C decreases the concentration of electrons to ∼1×1017 cm−3. The results obtained here indicate that this change in the free-electron concentration correlates qualitatively with the change in excess arsenic concentration in the layers. Fiz. Tekh. Poluprovodn. 33, 900–906 (August 1999)  相似文献   

6.
Low-temperature (LT) buffer-layer techniques were employed to improve the crystalline quality of ZnO films grown by molecular-beam epitaxy (MBE). Photoluminescence (PL) spectra show that CdO, as a hetero-buffer layer with a rock-salt structure, does not improve the quality of ZnO film grown on top. However, by using ZnO as a homo-buffer layer, the crystalline quality can be greatly enhanced, as indicated by PL, atomic force microscopy (AFM), x-ray diffraction (XRD), and Raman scattering. Moreover, the buffer layer grown at 450°C is found to be the best template to further improve the quality of top ZnO film. The mechanisms behind this result are the strong interactions between point defects and threading dislocations in the ZnO buffer layer.  相似文献   

7.
Growth by molecular-beam epitaxy (MBE) of the dilute-magnetic alloy GaMnN is reported. The Mn concentration, as determined by Auger electron spectroscopy (AES), is found to be linear with increasing Mn-cell temperature up to ∼43at.%Mn. No second phases are observed for Mn levels below 9 at.%. The cubic-phase Mn4N is found to be the thermodynamically stable phase at the growth conditions used to produce GaMnN. Hysteresis in M versus H is observed in both GaMnN and GaMnN:C grown on both sapphire and metal-oxide chemical-vapor deposition (MOCVD) GaN at several growth temperatures. Magnetotransport results show the anomalous Hall effect, negative magnetoresistance, and magnetic hysteresis, indicating that Mn is incorporating into the GaN and forming the ferromagnetic-semiconductor GaMNN. Room-temperature hysteresis is obtained in magnetization measurements with an optimum Mn concentration of ∼3 at.%.  相似文献   

8.
We report on the phase separation of Ga-doped MgZnO layers grown by plasma-assisted molecular-beam epitaxy. Based on X-ray diffraction, low-temperature (10 K) photoluminescence, and reflection high-energy electron diffraction observations, it is possible to classify the phase of Ga-doped MgZnO layers into three regions depending on the incorporated Ga concentration ([Ga]). Single-phase Mg0.1Zn0.9O layers are grown when [Ga] is less than 1×1018 cm−3. For [Ga] between 1×1018 cm−3 and 1×1020 cm−3, ZnO and Mg0.2Zn0.8O coexist, where electron transport is considered to be via two-channel conduction. When [Ga] exceeds 1×1020 cm−3, the Ga-doped MgZnO layers become polycrystalline, where carrier compensation takes place presumably due to grain boundaries.  相似文献   

9.
Defects in mercury-cadmium-telluride heteroepitaxial structures (with 0.3 to 0.4 molar fraction of cadmium telluride) grown by molecular-beam epitaxy on silicon substrates are studied. The low-temperature photoluminescence method reveals that there are comparatively deep levels with energies of 50 to 60 meV and shallower levels with energies of 20 to 30 meV in the band gap. Analysis of the temperature dependence of the minority carrier lifetime demonstrates that this lifetime is controlled by energy levels with an energy of ~30 meV. The possible relationship between energy states and crystal-structure defects is discussed.  相似文献   

10.
Molecular-beam epitaxy was used to grow distributed Bragg mirrors on ZnSe substrates. These mirrors are composed of 10.5 and 20 pairs of alternating quarter-wave ZnMgSe and ZnCdSe layers with reflectance peaks at the wavelengths of 530 and 560 nm, respectively, which fall in the transparency region of the substrate. These structures were studied by low-temperature cathodoluminescence, atomic-force microscopy, and transmission electron microscopy. The maximum of the reflection coefficient was 78% for a 20-pair mirror and 66% for a 10.5-pair mirror. This result is interpreted in terms of a model that takes into account the roughness of the interlayer boundaries.  相似文献   

11.
Intense highly polarized radiation from silicon nanostructures heavily doped with boron to 5 × 1021 cm−3 is studied as a function of temperature, forward current, and an additional lateral electric field. The features of the radiation intensity and degree of polarization suggest that an important role in the formation of the luminescence spectra is played by the ordered system of B+-B dipoles, formed as a result of the reconstruction of shallow boron acceptors as centers with negative correlation energy. The results obtained are interpreted within a proposed model based on two-electron adiabatic potentials, according to which radiation results from donor-acceptor recombination via boron dipole center states, involving shallow phosphorus donors.  相似文献   

12.
The electrical and optical properties of epitaxial CdHgTe films grown on silicon substrates by molecular-beam epitaxy have been studied. The results of photoluminescence measurements are indicative of the high structural perfection of the films, and Hall data combined with low-energy ion treatment point to a low concentration of residual donors (??5 × 1014 cm?3). Acceptor states supposedly related to the capture of impurities at structural defects typical of strongly lattice-mismatched heteroepitaxial structures are found in the films.  相似文献   

13.
The special features of redistribution of phosphorus implanted into silicon wafers with a high concentration of boron (N B=2.5×1020 cm?3) were studied. It is shown that, in silicon initially doped heavily with boron, the broadening of concentration profiles of phosphorus as a result of postimplantation annealing for 1 h in the temperature range of 900–1150°C is significantly less than in the case of lightly doped silicon. The results are interpreted in terms of the impurity-impurity interaction with the formation of stationary boron-phosphorus pairs. The binding energy of boron-phosphorus complexes in silicon was estimated at 0.6–0.8 eV.  相似文献   

14.
The photoluminescence spectra of (100) GaAs layers, both undoped and doped with silicon, is investigated at T=77 K. It is found that along with the B-band, which corresponds to interband radiative recombination, the spectra of doped layers also exhibit a so-called Si-band located near ⋍1.4 eV. In multilayer δ-doped structures, an additional band appears in the region ⋍1.47–1.48 eV, which is called here the δ-band. The dependence of the energy positions, intensities, and shapes of these photoluminescence bands on the doping dose N Si, laser excitation power, and temperature are investigated. It is shown that the Si-band is caused by optical transitions between the conduction band and a deep acceptor level (∼100 meV) connected with Si atoms on As sites. It is also established that the dependences of the shape and intensity of the δ-band on temperature and photoluminescence excitation power are identical to the corresponding dependences for the B-band. The behavior of the δ-band in the photoluminescence spectra is viewed as evidence of quantum-well effects in the δ-doped structures. Fiz. Tekh. Poluprovodn. 32, 1060–1063 (September 1998)  相似文献   

15.
The results of an investigation of the structural perfection of GaAs epitaxial films grown by molecular-beam epitaxy at low growth temperatures (240–300 °C) and various As/Ga flux ratios (from 3 to 13) are presented. Diffraction reflection curves display characteristic features for the samples before and after annealing in the temperature range from 300 to 800 °C. Hypotheses which account for these features are advanced. The range of variation of the arsenic/gallium flux ratio, in which low-temperature growth takes place under nearly stoichiometric conditions, is established. Fiz. Tekh. Poluprovodn. 31, 1168–1170 (October 1997)  相似文献   

16.
Temperature dependences of the concentration and electron Hall mobility in Si:Er/Sr epitaxial layers grown at T = 600°C and annealed at 700 or 900°C have been investigated. The layers were grown by sublimation molecular-beam epitaxy in vacuum (~10?5 Pa). The energy levels of Er-related donor centers are located 0.21–0.27 eV below the bottom of the conduction band of Si. In the range 80–300 K, the electron Hall mobility in unannealed Si:Er epitaxial layers was lower than that in Czochralski-grown single crystals by a factor of 3–10. After annealing the layers, the fraction of electron scattering from Er donor centers significantly decreases.  相似文献   

17.
Epitaxial silicon layers codoped with erbium and oxygen were grown by molecular-beam epitaxy using a silicon sublimation source. For growing the erbium-doped silicon layers, two types of impurity sources were used: (i) erbium-doped silicon plates were used as a source of fluxes of Er and Si atoms; and (ii) metallic erbium plates were used as an impurity-vapor source in combination with the silicon sublimation source. If gaseous oxygen was used for in situ codoping with erbium and oxygen, then concentrations ranging from 1018 to 1020 cm?3 were attained. When oxygen is in the growth chamber, the erbium-entrapment efficiency of a layer increases substantially, with the surface segregation of erbium also being suppressed by oxidation.  相似文献   

18.
The substrate growth temperature dependence of electrical properties for a low-noise MESFET fabricated on MBE-grown material has been demonstrated. The optimum noise figure and its associated gain were attributed to the higher epilayer quality and mobility at a growth temperature of 650°C between temperatures of 550°C and 700°C.  相似文献   

19.
The dependence of the concentrations of the Er impurity and ionized donors on the epitaxy temperature has been studied before and after annealing of Si:Er/Si layers grown by sublimation molecular-beam epitaxy. n-Si:Er layers have been grown in the temperature range 400–800°C and annealed in hydrogen atmosphere at a temperature of 800°C for 30 min. The possible nature of the donor centers is discussed.  相似文献   

20.
Electrically active centers in light-emitting Si:Er layers grown by sublimation molecular-beam epitaxy (SMBE) on single-crystal Si substrates have been investigated by admittance spectroscopy with temperature scanning and by DLTS. The total density of electrically active centers is defined by shallow donor centers with ionization energies of 0.016–0.045 eV. The effect of growth conditions and post-growth annealing on the composition and density of electrically active centers has been studied. Significant differences in composition of the electrically active centers with deep levels and in channels of energy transfer from the electron subsystem of a crystal to Er3+ ions between Si:Er layers grown by SMBE and ion implantation have been revealed.  相似文献   

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