Showing papers on "Epitaxy published in 1984"
TL;DR: GexSi1−x films are grown on Si by molecular beam epitaxy and analyzed by Nomarski optical interference microscopy, Rutherford ion backscattering and channeling, x-ray diffraction, and transmission electron microscopy as discussed by the authors.
Abstract: GexSi1−x films are grown on Si by molecular beam epitaxy and analyzed by Nomarski optical interference microscopy, Rutherford ion backscattering and channeling, x‐ray diffraction, and transmission electron microscopy. The full range of alloy compositions will grow smoothly on silicon. GexSi1−x films with x≤0.5 can be grown free of dislocations by means of strained‐layer epitaxy where lattice mismatch is accommodated by tetragonal strain. Critical thickness and composition values are tabulated for strained‐layer growth. Multiple strained layers are combined to form a GexSi1−x/Si strained‐layer superlattice.
675 citations
TL;DR: In this article, the Schottky-barrier heights of NiSi2layers grown under ultrahigh-vacuum conditions on n-type Si(111) are found to be 0.65 and 0.79 eV for type-A and type-Bepitaxial systems, respectively.
Abstract: Electrical behaviors at two single-crystal metal-semiconductor interfaces are studied. Schottky-barrier heights of NiSi2layers grown under ultrahigh-vacuum conditions on n- type Si(111) are found to be 0.65 and 0.79 eV for type-Aand type-Bepitaxial systems, respectively. These results are compared with the proposed theoretical models of Schottky barriers.
364 citations
TL;DR: In this article, temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped layers grown by molecular-beam epitaxy over the entire composition range.
Abstract: Temperature-dependent Hall-effect measurements were carried out both in dark and in ambient light on Si-doped ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ layers grown by molecular-beam epitaxy over the entire composition range. Above 150 K, the measured Hall carrier densities (different from actual electron densities near the direct-indirect transition) show an exponential dependence on temperature. A shallow donor (\ensuremath{\le}15 meV) tied to the $\ensuremath{\Gamma}$ band and a deep donor level tied to the $L$ band were observed. The deep donor is dominant for $xg0.2$, and its activation energy ${E}_{d}$ rises dramatically up to the direct-indirect band-gap crossover and peaks at 160 meV for $x\ensuremath{\sim}0.48$. As the A1 fraction increases further, ${E}_{d}$ decreases, reaching 57 meV for AlAs. The error due to multivalley conduction on the measured values of ${E}_{d}$ is shown to be negligible. The variation in ${E}_{d}$ of the dominant donor level with $x$ is accounted for by our theoretical calculations using a multivalley effective-mass model. A decrease of ${E}_{d}$ with increasing doping densities is also observed. At high substrate-growth temperature, the incorporation of Si atoms was found to decrease. The persistent-photoconductivity (PPC) effect was observed with an increase in mobilities over the dark values in the entire composition range. The effect was most pronounced in the range $0.20\ensuremath{\le}x\ensuremath{\le}0.40$. Traps related to the Si-doping density appear to be responsible for the observed photoconductivity effect. The ratio of the PCC traps and the Si atomic density is maximum at $x\ensuremath{\sim}0.32$ and is minimum in the direct-indirect band-gap crossover region.
312 citations
TL;DR: In this paper, a beam epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs.
Abstract: A new epitaxial growth technique, chemical beam epitaxy (CBE), was demsonstrated and investigated with the growth of InP and GaAs. In this technique, all the sources were gaseous group III and group V alkyls. The In and Ga were derived by the pyrolysis of either trimethylindium or triethylindium and trimethylgallium or triethylgallium at the heated substrate surface, respectively. The As2 and P2 were obtained by thermal decomposition of triethylphosphine and trimethylarsine in contact with heated Ta or Mo at 950–1200 °C, respectively. Unlike conventional vapor phase epitaxy, in which the chemicals reach the substrate surface by diffusing through a stagnant carrier gas boundary layer above the substrate, the chemicals in CBE were admitted into a high vacuum growth chamber and impinged directly light of sight onto the heated substrate surface in the form of molecular beams. The beam nature of CBE resulted in efficient use of the impinging chemicals and allowed the utilization of mechanical shutters. A gas h...
226 citations
TL;DR: The van der Waals epitaxy can be realized in the materials having no dangling bonds on their clean surfaces, on which epitaxial growth proceeds by the van derWaals force as mentioned in this paper.
219 citations
TL;DR: In this article, a new method for growing cadmium mercury telluride (CMT) is described where alternate thin layers of CdTe and HgTe are grown by metalorganic vapour phase epitaxy (MOVPE) and allowed to interdiffuse at the growth temperature.
218 citations
TL;DR: In this paper, the epitaxial growth of GaAs and AlGaAs on (100) oriented Si substrates by molecular beam epitaxy was studied in situ by reflection high-energy electron diffraction.
Abstract: We have grown GaAs and AlGaAs on (100) oriented Si substrates by molecular beam epitaxy. The epitaxial growth was studied in situ by reflection high‐energy electron diffraction. Low‐temperature photoluminescence, Raman scattering, and scanning electron microscopy were used to characterize the epitaxial layers. It is shown for the first time that antiphase disorder could be suppressed. The doped AlGaAs grown directly on Si substrates exhibited PL efficiency similar to that of AlGaAs grown on GaAs substrates.
213 citations
TL;DR: In this article, a single-crystal Si-Ge structure for photodetector in the wavelength region of up to 1.5 µm has been reported, where the top three layers form a germanium p-i-n diode which is removed from the Ge-Si interface by a buffer layer of high conductivity.
Abstract: We report a single-crystal Si-Ge structure which works as an efficient photodetector in the wavelength region of up to 1.5 µm. The multilevel structure is grown by molecular-beam epitaxy on an n-type 3-in silicon substrate and consists of the following layers: n+silicon (1000 A), n+Ge x Si 1 - x alloy (1800 A, graded in ten steps from x = 0 to x = 1 ), n+germanium (1.25 µm), undoped germanium (2.0 µm), and p+germanium (2500 A). Top three layers form a germanium p-i-n diode, which is removed from the Ge-Si interface by a buffer layer of high conductivity. An advantage of this structure is that its performance is insensitive to material defects in the buffer layers. Moreover, transmission electron microscopy shows that the density of dislocations introduced by lattice mismatch at the Ge-Si interface falls off with the separation from the interface. Our first experimental structures do exhibit the characteristics of a germanium p-i-n diode. The spectral response curves agree with those given in the literature for germanium, both at room and liquid nitrogen temperatures. For the incident light wavelength of 1.45 µm we have measured a quantum efficiency of 41 percent at T = 300 K. we believe that our approach opens an attractive possibility of fabricating complete infrared optoelectronic systems on a silicon chip.
177 citations
TL;DR: In this article, a 360-nm-thick Al film was deposited on clean Si(111 and Si(100) by ionized-cluster beam at room temperature, and its crystaline orientation was studied by reflection electron diffraction during and after the deposition.
Abstract: Epitaxial Al films were deposited on clean Si(111) and Si(100) by ionized‐cluster beam at room temperature. Crystalline orientation was studied by reflection electron diffraction during and after the deposition of the 360‐nm‐thick Al films. Ion channeling spectra, optical reflectance spectra, and scanning electron micrographs were taken to evaluate the properties of the deposited films and to elucidate the effects of acceleration of ionized clusters. It was found that the films did not give rise to hillock and alloy penetration at the interface after 450 °C thermal treatment.
160 citations
TL;DR: In this paper, a neon ion beam has been used to regrow epitaxially a ~1700-AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures.
Abstract: A neon ion beam has been used to regrow epitaxially a ~1700-\AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures. The damaged layer was produced by implanting 80-keV silicon ions to a dose of $2\ifmmode\times\else\texttimes\fi{}{10}^{15}$ ions/${\mathrm{cm}}^{2}$ at room temperature. The channeling technique with 315-keV protons was used to investigate the depth distribution of the damage, and disorder depth profiles were extracted from the backscattering spectra using calculations based on multiplescattering theory. The epitaxial regrowth was quantitatively determined from the extracted profiles. Many of the parameters which influence the regrowth rate, such as dose, dose rate, target temperature, energy, and random or channeled direction for the annealing beam, were varied. The results were compared with energy deposition calculations which indicated strongly that the annealing rate depends on the energy deposited in elastic collisions by the annealing ion beam. A defect annealing model based on vacancy diffusion is discussed.
133 citations
TL;DR: In this article, Mirror-like monocrystalline epitaxial layers of GaAs were easily obtained on a GaAs substrate at the substrate temperature of 530-630°C.
Abstract: Crystal growth of GaAs using trimethylgallium (TMG) as a Ga source in a molecular beam epitaxial system has been studied. Mirror‐like monocrystalline epitaxial layers of GaAs were easily obtained on a GaAs substrate at the substrate temperature of 530–630°C. Epitaxial layers were p type and the carrier concentration of these films was about 1018–1019 cm−3. In particular, no deposition was observed on a SiO2 film in this TMG‐As4 system. This feature showed the possibility of selective epitaxy of GaAs.
TL;DR: The Hall effect and resistivity have been measured in liquid phase-epitaxial (LPE) HgCdTe layers in the temperature range between 16 and 300 K.
Abstract: The Hall effect and resistivity have been measured in liquid‐phase‐epitaxial (LPE) HgCdTe layers in the temperature range between 16 and 300 K. The composition of the material covers the wavelength range from 3 to 12 μm. The results obtained from a broad sample base have been systematically analyzed and categorized. Although much of the data follows classical behavior and is readily understood, it has now become possible to analyze quantitatively the variety of other observed Hall‐effect data in some of the LPE HgCdTe layers by making use of a theoretical model for multilayer structure. This allows such fundamental properties as surface charge density, bulk carrier concentration, surface and bulk mobility, and dopant concentration in double‐layer heterojunctions to be extracted from the experimental data otherwise classified as ‘‘anomalous’’ and not analyzable previously. Controlled experiments have been carried out to show the dependence of Hall‐effect measurements on layer thicknesses and various surfac...
TL;DR: In this article, the authors investigated the electrical properties of 3C-SiC layers at the temperatures between room temperature and 850 °C and found that the electron mobility changes with temperature as μH∼T−1.2∼− 1.4.
Abstract: Electrical properties of 3C‐SiC layers, epitaxially grown on silicon by chemical vapor deposition, have been investigated at the temperatures between room temperature and 850 °C. In this temperature range, the electron mobility changes with temperature as μH∼T−1.2∼−1.4. The weaker temperature dependence of mobility and the larger mobilities compared with other polytypes of SiC suggest that 3C‐SiC is a promising material for devices operated at high temperatures.
TL;DR: In this paper, a set of superlattices of the dilute magnetic semiconductor Cd1−x Mnx Te (x∼0.2) alternating with CdTe have been successfully grown for the first time using the molecular beam epitaxy technique.
Abstract: Single‐crystal multilayers of the dilute magnetic semiconductor Cd1−x Mnx Te (x∼0.2) alternating with CdTe have been successfully grown for the first time using the molecular beam epitaxy technique. Four sets of superlattices have been prepared consisting of 14, 60, 90, and 240 double layers of average thickness 460, 140, 75, and 37 A, respectively. Each set consists of two samples grown simultaneously using 7×15×1‐mm thick (0001) sapphire substrates onto which 5.0‐μm‐thick CdTe buffer layers were first deposited. X‐ray diffraction techniques were employed to verify that epitaxy had been achieved and to obtain the average lattice constant of each of the multilayer structures. X‐ray diffraction satellites were observed on both sides of the (111) diffraction peak of the superlattices composed of 14 and 60 alternating layers, respectively, which allowed an accurate estimate of the superlattice period, or double‐layer thickness, for these samples. Results of UV reflectance studies and photoluminescence experi...
Patent•
10 May 1984TL;DR: In this paper, a monocrystalline silicon layer is formed on a mask layer on a semiconductor substrate, and an epitaxial layer is then grown by a two-step deposition/etching cycle.
Abstract: A monocrystalline silicon layer is formed on a mask layer on a semiconductor substrate. An apertured mask layer is disposed on the substrate, and an epitaxial layer is then grown by a two-step deposition/etching cycle. By repeating the deposition/etching cycle a predetermined number of times, monocrystalline silicon will be grown from the substrate surface, through the mask aperture, and over the mask layer.
TL;DR: In this article, the growth of epitaxial (100) CdTe films on GaAs substrates by molecular beam epitaxy was discussed, and X-ray diffraction, UV reflectance, photoluminescence, and transmission electron microscopy techniques were employed to characterize the film specimens.
Abstract: Growth of epitaxial (100) CdTe films on (100) GaAs substrates by molecular beam epitaxy is discussed. X‐ray diffraction, UV reflectance, photoluminescence, and transmission electron microscopy techniques were employed to characterize the film specimens. The high structural perfection of the layers was evidenced by line dislocation densities of ≤104/cm2 at the free surface of films ≂6.6 μm thick and by measurable excitonic photoluminescence (∼1.504 eV) at room temperature. The CdTe epilayers were smooth and mirrorlike in appearance.
TL;DR: In this article, the surfaces of epitaxial CaF2 layers grown on (100 and (111) Si by molecular beam epitaxy have been studied using scanning electron microscopy.
Abstract: The surfaces of epitaxial CaF2 layers grown on (100) and (111) Si by molecular beam epitaxy have been studied using scanning electron microscopy. The (111) surface exhibits small triangular hillocks, while the (100) surface exhibits a columnar structure. This latter structure can be accounted for by the prohibitively large free energy of the (100) surface. A dipole moment exists perpendicular to this surface which causes the electrostatic energy to diverge. This phenomenon explains the inferior (100) growth as compared to (111) and has important implications for possible applications of group II‐A fluoride/semiconductor epitaxial structures.
TL;DR: In this article, the metastable alloys covering this entire composition range have been grown by organometallic vapor phase epitaxy (OMVPE) using trimethyl gallium, antimony and -arsenic as the source materials.
Abstract: The system GaAs1−xSbx has a solid phase miscibility gap ranging from x = 0.2 to x = 0.8 at the typical growth temperature of 600 C; however, metastable alloys covering this entire composition range have been grown by organometallic vapor phase epitaxy (OMVPE) using trimethylgallium, antimony and -arsenic as the source materials. The solid composition is studied for various values of growth temperature, the ratio of Sb to total group V elements in the vapor phase and the ratio of group III to group V elements in the vapor phase. The fraction of trimethylarsenic (TMAs) pyrolyzed in the vapor phase is found to be < 1 and to vary with temperature. Taking into account the incomplete pyrolysis of TMAs, solid composition is found to be controlled by thermodynamics. The effects of temperature and vapor composition are all accurately predicted using a simple thermodynamic model assuming equilibrium to be established at the solid-vapor interface. The properties of these metastable GaAs1−x Sbx alloys were explored using interference contrast microscopy, room temperature and 4 K photoluminescence, Hall effect and conductivity measurements. The alloy GaAs0.5Sb0.5 grown lattice matched to the InP substrate has excellent surface morphology, is p-type, and the photoluminescence spectrum consists of a single, intense, fairly broad (23.5 meV half width) peak at a wavelength of 1.54 Μm.
TL;DR: The use of P2 and As2 beams generated by several different beam sources for the growth of InP, GaAs, and GaxIn1−xPyAs1−y has been investigated in this paper.
Abstract: The use of P2 and As2 beams generated by several different beam sources for the growth of InP, GaAs, and GaxIn1−xPyAs1−y has been investigated. Accommodation coefficients for As2 and P2 were determined for heated GaAs and InP surfaces. It is demonstrated that a source utilizing decomposition of the hydrides over the range 200–2000 Torr and providing a leak of the resulting P2, As2, and H2 molecules into a molecular beam epitaxy (MBE) system can be used for the growth of GaxIn1−xPyAs1−y layers lattice matched to InP. Heterostructure lasers emitting at 1.5 μm with room temperature threshold current densities of 2000 A/cm2 and differential quantum efficiencies of 17%–19% were fabricated to demonstrate the quality of the epitaxy by this method. Initial studies of the cracking of AsH3 and PH3 at low pressures in contact with heated Ta suggest that Ta acts as a catalyst for the decomposition and that low pressure beam sources may also be useful for gas source MBE.
TL;DR: In this paper, the first fabrication of metal-epitaxial insulator-semiconductor field effect transistors by molecular beam epitaxial growth of CaF2 on Si is reported.
Abstract: Fabrication of metal‐epitaxial insulator‐semiconductor field‐effect transistors by molecular beam epitaxial growth of CaF2 on Si is reported for the first time. These devices have a room‐temperature electron mobility of 300 cm2/Vs and a threshold voltage of 0.5 V. The breakdown voltage of the films ranges from ≳105 to ≳106 V/cm in different regions of the film. These devices will be important for the characterization and improvement of the interface transport properties of the CaF2/Si system.
TL;DR: Light-emitting diodes have been fabricated in GaAs grown by metalorganic chemical vapor deposition on vapordeposited epitaxial Ge films on Si substrates as mentioned in this paper.
Abstract: Light‐emitting diodes have been fabricated in GaAs grown by metalorganic chemical vapor deposition on vapor‐deposited epitaxial Ge films on Si substrates. The light‐emitting junction was formed by zinc diffusion into the n‐type GaAs layer. Room‐temperature light emission centered at 872 nm has been observed.
TL;DR: In this article, the authors reviewed the recent progress in the area of high-quality epitaxial growth of GaAs and GaAlAs and pointed out the important problems which remain unsolved.
Journal Article•
TL;DR: In this paper, the authors describe the interdisciplinary research effort that led to the breakthrough which enabled the room temperature operation of semiconductor lasers, which was the beginning of a new era in semiconductor devices.
Abstract: The demonstration of CW room temperature operation of the heterostructure laser was the beginning of a new era in semiconductor devices. This era introduced the use of heterojunctions to create electrical as well as optical boundaries. New developments in epitaxial techniques provided the base for heterojunction devices. This work describes the interdisciplinary research effort that lead to the breakthrough which enabled the room temperature operation of semiconductor lasers.
Patent•
25 Jun 1984TL;DR: In this article, a selective epitaxial growth method for forming an opening, utilizing anisotropic dry etching, in a silicon oxide film formed on a silicon substrate and epitaxially growing a silicon layer selectively in the opening is presented.
Abstract: Disclosed herein is a selective epitaxial growth method for forming an opening, utilizing anisotropic dry etching, in a silicon oxide film formed on a silicon substrate and epitaxially growing a silicon layer selectively in the opening. The anisotropic dry etching is performed employing a mixed gas of carbon tetrafluoride and hydrogen, and the wall surface of the opening is perpendicular to the major surface of the silicon substrate. The epitaxial growth is achieved under a temperature of 900° to 1100° C. utilizing a mixed gas of a low pressure under 100 Torr. containing dichlorosilane as a silicon source and hydrogen as a carrier gas. A silicon layer thus obtained contains substantially no lattice defects such as a stacked fault.
TL;DR: The epitaxial layers of GaN have been grown on (0001)oriented sapphire substrates using metalorganic chemical vapor deposition as discussed by the authors, and two kinds of blue electroluminescence were observed at room temperature with exciting voltage of 4-8 V with emission wavelength of 430 and 488 nm.
Abstract: The epitaxial layers of GaN have been grown on (0001)‐oriented sapphire substrates using metalorganic chemical vapor deposition. The layers with good quality and relatively smooth surface morphology were obtained by enforcing growth in H2 after adherence of nuclei to the substrates in N2 atmosphere. Using this technique, GaN light emitting diodes with metal‐insulating n‐type structure were fabricated. Two kinds of blue electroluminescence were observed at room temperature with exciting voltage of 4–8 V with emission wavelength of 430 and 488 nm. The external efficiency is about 0.005%.
Book•
01 Jul 1984
TL;DR: In this article, a detailed analysis of NTD-Silicon Rod, slice resistivity, and Annealing effects on high-voltage Direct-Current Thyristors is presented.
Abstract: 1: NonSilicon NTD Materials.- Neutron Transmutation Doping of p-Type Czochralski-Grown Gallium Arsenide.- NTD Germanium: A Novel Material for Low Temperature Bolometers.- Reliable Identification of Residual Donors in High Purity Epitaxial Gallium Arsenide by Transmutation Doping.- Spallation Neutron Damage in Group IV, III-V and II-VI Semiconductors at 5 K.- 2: Irradiation Technology.- Future Reactor Capacity for the Irradiation of Silicon.- An Automatic Controlled, Heavy Water Cooled Facility for Irradiation of Silicon Crystals in the DR 3 Reactor at Riso National Laboratory, Denmark.- Irradiation of Single Silicon Crystals with Diameters in the 3- to 5-Inch Range in French Reactors.- The Development of NTD Technology in the Institute of Atomic Energy.- Measurements of the Gamma Abundance of Silicon-31.- Experiences with the Norwegian Research Reactor JEEP II in Neutron Transmutation Doping.- 3: Practical Utilizaton of NTD Material.- The Development of the Market for Neutron Transmutation Doped Silicon.- Neutron Transmutation Doped Silicon for Power Semiconductor Devices.- Process Induced Recombination Centres in Neutron Transmutation Doped Silicon and Their Influence on High-Voltage Direct-Current Thyristors.- A Study of Float-Zoned NTD Silicon Grown in a Hydrogen Ambient.- Experience with Neutron Transmutation Doped Silicon in the Production of High Power Thyristors.- 4: Characterization of NTD Material.- Transient Current Spectroscopy of Neutron Irradiated Silicon.- Calibration of the Photoluminescence Technique for Determination of Phosphorus in Silicon by Neutron Transmutation Doping.- Swirls in Neutron-Transmutation Doped Float-Zoned Silicon.- Compensation Effects in N.T.D. Indium Doped Silicon.- Correlation of NTD-Silicon Rod, Slice Resistivity.- 5: Neutron Damage and Annealing.- A Detailed Annealing Study of NTD Silicon Utilizing Raman Scattering.- Annealing Study of NTD Silicon Doped with Boron.- Annealing Effects of NTD Silicon on High-Power Devices.- Study of Annealing Behavior and New Donor Formation in Neutron Transmutation Doped Silicon Grown in a Hydrogen Atmosphere.- Participants.
TL;DR: In this article, the growth of GaAs/(Ca, Sr) F2/GaAs structures by means of molecular beam epitaxy has been demonstrated and it has been shown that it was possible to grow layers with good crystalline quality and no noticeable interdiffusion at the interfaces.
Abstract: Epitaxial growth of GaAs/(Ca, Sr) F2/GaAs structures by means of molecular beam epitaxy has been demonstrated. It has been shown that it was possible to grow layers with good crystalline quality and no noticeable interdiffusion at the interfaces. In addition, the uppermost GaAs layers present interesting electrical properties, exhibiting electron Hall mobilities of about 1300 cm2/Vs.
Patent•
26 Nov 1984
TL;DR: Localized epitaxial growth of GaAs from a silicon monocrystalline substrate to provide a three-dimensional Si-GaAs structure and method is described in this paper, where the silicon has an insulating layer deposited thereover and a window is opened through the layer to expose a small area of the underlying silicon from which silicon is epitaxially grown until the window is nearly full whereupon a thin buffer layer such as germanium is used over the epi-silicon to fill the window.
Abstract: Localized epitaxial growth of GaAs from a silicon monocrystalline substrate to provide a three-dimensional Si-GaAs structure and method. The silicon has an insulating layer deposited thereover and a window is opened through the layer to expose a small area of the underlying silicon from which silicon is epitaxially grown until the window is nearly full whereupon a thin buffer layer such as germanium is epitaxially grown over the epi-silicon to fill the window. Al x Ga 1-x As (where x≧0) is then locally epitaxially grown from the buffer layer and it grows laterally as well as vertically to cover the surrounding insulating layer surface and provide a site for high frequency electronics.
Patent•
15 Jun 1984TL;DR: In this article, a method for achieving extreme and arbitrary doping profiles in semiconductors with dopant concentrations varying over orders of magnitude in a few atomic layers is proposed, which involves evaporating the semiconductor along with the desired amounts of n- or p- dopants onto an atomically clean substrate semiconductor surface in an ultrahigh vacuum environment at low temperatures such that an amorphous film results.
Abstract: A method for achieving extreme and arbitrary doping profiles in semiconductors with dopant concentrations varying over orders of magnitude in a few atomic layers The method involves evaporating the semiconductor, along with the desired amounts of n- or p- dopants onto an atomically clean substrate semiconductor surface in an ultrahigh vacuum environment at low temperatures such that an amorphous film results The amorphous film is then crystallized epitaxially by a solid phase epitaxy, thereby providing a single crystal with the desired dopant profile Multiple profile changes or grading may be included in the semiconductor film by varying dopant concentrations in the amorphous layer as desired