Atomic layer epitaxy (ALE) of device quality AlGaAs and AlAs has been demonstrated.on a modified ... more Atomic layer epitaxy (ALE) of device quality AlGaAs and AlAs has been demonstrated.on a modified commercial metalorganic vapor phase epitaxial (MOVPE) reactor with a rotating susceptor. AlAs had a much narrower plateau of saturated growth as compared to GaAs and
Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high tem... more Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high temperature annealing in SiH4. Characterization via AES, EELS, LEED, XPS, and UPS was conducted. At T greater than 850 C, the surface oxide was rapidly removed. Exposure to approx. 400 Langmuir (10(exp -6) Torr(dot)liter/s) of SiH4 resulted in complete surface oxide removal and a nearly stoichiometric (l x l) 6H-SiC surface suitable for ALE of SiC. Further exposure resulted in a (3 x 3)R30 deg Si-rich reconstructed surface. Subsequent annealing in UHV resulted in a (square root of 3 x square root of 3)R30 deg Si deficient/graphitic reconstructed surface. The first set of wafers containing HBT device structures were fabricated on SiC films grown via ALE. No transistor activity was detected. Electrical characterization and SEM showed the most likely fault to be inaccurate etching of the SiC emitter. Nucleation and growth of oriented diamond particles on seeded, group of zone axes (0001) oriented single crystal Co substrates was achieved via multi-step, hot-filament CVD process involving seeding, annealing, nucleation and growth. Diamond particles oriented group of zone axes (111) were obtained. Micro-Raman showed a FWHM of 4.3/cm. A very weak graphitic peak was observed on regions of the substrate not covered by the diamond particles. A nucleation model has been proposed. Initial results showed that CeO2 film grows epitaxially on (111) Si substrates. The CeO2 films had density of interfacial traps and fixed oxide charge values comparable to that of amorphous SiO2/Si.
We report on a Raman study of several Ga 1-x In x P samples grown by atomic layer epitaxy. The Ga... more We report on a Raman study of several Ga 1-x In x P samples grown by atomic layer epitaxy. The Ga 1-x In x P LO-phonon Raman peaks are present in the z(xx)z¯ (polarized) spectrum as well as the z(xy)z¯ (depolarized) spectrum, in contradiction to the usual selection rules for ...
The potential applications of Atomic Layer Epitaxy of HI-V compounds will be outlined. These incl... more The potential applications of Atomic Layer Epitaxy of HI-V compounds will be outlined. These include the growth of special structures and devices such as ordered alloys, ultra-thin quantum wells, non-alloyed contacts, planar doped FET's and HBT's. Also, the main challenges facing ALE will be outlined along with possible solutions. These include reactor design, control of carbon doping and the growth of ternary alloys. A general assessment of the ALE technology will be provided.
Dilute Magnetic Semiconductor (DMS) research has mainly focused on II−VI and III−V materials, whe... more Dilute Magnetic Semiconductor (DMS) research has mainly focused on II−VI and III−V materials, where a maximum Curie temperature (T C) of 110K was reported in (Ga,Mn)As.[1] However, (Ga,Mn)N has shown ferromagnetic behavior with Curie temperature (T C) exceeding room temperature. [2] ,[3],[4] The elevated Curie temperatures exhibited in this material has obvious and practical technological implications. Efforts to grow (Ga,Mn)N by metal−organic chemical vapor deposition (MOCVD) have produced much information on the optical properties of the films. Korotkov[5] et al. shows that Mn forms a deep acceptor level with optical transitions at 1.4 and 2.06 eV, and photoluminescence measurements of Mn−doped films indicated the presence of an intra 3d−shell transition of the Mn ion. However, there were no reports on the magnetic properties or crystalline quality of this material system grown by MOCVD. The purpose of this study is to demonstrate room temperature ferromagnetic MOCVD grown (Ga,Mn)...
The principal objective of research conducted under this contract during the past twelve months h... more The principal objective of research conducted under this contract during the past twelve months has been the development and fabrication of two junction cascade solar cells in two different III-V semiconductor materials systems: AlGaAs/GaAs and AlGaAsSb/GaAsSb. Liquid phase epitaxy (LPE) has been successfully used to fabricate experimental cascade cells in both of these materials systems. Additional research has been carried out using organometallic/chemical vapor deposition (OM/CVD) growth technology.
2000 IEEE International Symposium on Compound Semiconductors. Proceedings of the IEEE Twenty-Seventh International Symposium on Compound Semiconductors (Cat. No.00TH8498), 2000
Six types of systematic photoluminescence (PL) surements (T ≥ 77 K) were carried out on single cr... more Six types of systematic photoluminescence (PL) surements (T ≥ 77 K) were carried out on single crystals of AlxGa1-xAs (x ~ 0.3) undoped or doped with Be by LPE or ion implantation. The multimea-surements approach was employed in order to ascertain that the highest-energy radiative recombination was in fact band-to-band (BTB), and consequently to obtain accurate activation energies. LPE doped
Cascade solar cells may now be the only promising approach to achieve high conversion efficiency;... more Cascade solar cells may now be the only promising approach to achieve high conversion efficiency; however, several technical problems have to be solved first. It is hoped that enough effort and time will be given to this structure so that an efficiency of over 30% can be achieved. Organometallic chemical vapor deposition seems to be the most suitable growth technique for this structure. Thus, it is suggested that current activities should be directed to solve problems associated with this technique.
ABSTRACTAtomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology h... more ABSTRACTAtomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology has grown in recent years because of potential applications to nanometer-order structures as well as to monolayer/cycle growth with high-uniformity in growth thickness, and to excellent selective-area growth. Recent developments in chloride ALE of various compounds and heterostructures are described. Potentials of ALE for producing such fine structures are shown.
Abstract We report the first demonstration of an AlGaAs/GaAs resonant tunneling diode (RTD) grown... more Abstract We report the first demonstration of an AlGaAs/GaAs resonant tunneling diode (RTD) grown by atomic layer epitaxy (ALE) which features room temperature negative differential resistance. The ALE growth is obtained in a rotating susceptor system with trimethylgallium, trimethylaluminum and arsine sources. Wafer mapping of the RTD properties indicates that monolayer thickness control can be achieved by this technique. In addition to vertical resonant tunneling, we also describe the application of ALE to realize ...
Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high tem... more Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high temperature annealing in SiH4. Characterization via AES, EELS, LEED, XPS, and UPS was conducted. At T greater than 850 C, the surface oxide was rapidly removed. Exposure to approx. 400 Langmuir (10(exp -6) Torr(dot)liter/s) of SiH4 resulted in complete surface oxide removal and a nearly stoichiometric (l x l) 6H-SiC surface suitable for ALE of SiC. Further exposure resulted in a (3 x 3)R30 deg Si-rich reconstructed surface. Subsequent annealing in UHV resulted in a (square root of 3 x square root of 3)R30 deg Si deficient/graphitic reconstructed surface. The first set of wafers containing HBT device structures were fabricated on SiC films grown via ALE. No transistor activity was detected. Electrical characterization and SEM showed the most likely fault to be inaccurate etching of the SiC emitter. Nucleation and growth of oriented diamond particles on seeded, group of zone axes (0001) orien...
Correlation between structural defects and appearance of multiple cathodoluminescence and photolu... more Correlation between structural defects and appearance of multiple cathodoluminescence and photoluminescence peaks of In x Ga 1-x N grown nominally with x=0.1 and increasing layer thickness (100 nm to 1000 nm) is discussed. Cathodoluminescence studies were performed on the cross-section samples earlier characterized by electron microscopy including Zcontrast microscopy. Strained and relaxed layers with different In concentrations were observed for InGaN layers above the critical layer thickness. Stacking faults appear at high density in the relaxed layer which also roughens, created a sawtooth surface profile due to V-shaped pits. Large domains of closely separated stacking faults (polytype-like) were observed. In Z-contrast microscopy stacking faults in upper/lower part of the layer appear with higher/lower brightness, suggesting different amount of In incorporation in agreement with x-ray and RBS results. Only thin, strained In-GaN layers showed single band-edge CL peaks. Multiple CL peaks appear in the relaxed, defective portion of the InGaN layers. By comparison with GaN samples where structural defects are associated with CL peak shifts, we postulate that defects, their type and distribution are main contributors to the multiple peaks observed for InGaN samples.
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Atomic layer epitaxy (ALE) of device quality AlGaAs and AlAs has been demonstrated.on a modified ... more Atomic layer epitaxy (ALE) of device quality AlGaAs and AlAs has been demonstrated.on a modified commercial metalorganic vapor phase epitaxial (MOVPE) reactor with a rotating susceptor. AlAs had a much narrower plateau of saturated growth as compared to GaAs and
Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high tem... more Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high temperature annealing in SiH4. Characterization via AES, EELS, LEED, XPS, and UPS was conducted. At T greater than 850 C, the surface oxide was rapidly removed. Exposure to approx. 400 Langmuir (10(exp -6) Torr(dot)liter/s) of SiH4 resulted in complete surface oxide removal and a nearly stoichiometric (l x l) 6H-SiC surface suitable for ALE of SiC. Further exposure resulted in a (3 x 3)R30 deg Si-rich reconstructed surface. Subsequent annealing in UHV resulted in a (square root of 3 x square root of 3)R30 deg Si deficient/graphitic reconstructed surface. The first set of wafers containing HBT device structures were fabricated on SiC films grown via ALE. No transistor activity was detected. Electrical characterization and SEM showed the most likely fault to be inaccurate etching of the SiC emitter. Nucleation and growth of oriented diamond particles on seeded, group of zone axes (0001) oriented single crystal Co substrates was achieved via multi-step, hot-filament CVD process involving seeding, annealing, nucleation and growth. Diamond particles oriented group of zone axes (111) were obtained. Micro-Raman showed a FWHM of 4.3/cm. A very weak graphitic peak was observed on regions of the substrate not covered by the diamond particles. A nucleation model has been proposed. Initial results showed that CeO2 film grows epitaxially on (111) Si substrates. The CeO2 films had density of interfacial traps and fixed oxide charge values comparable to that of amorphous SiO2/Si.
We report on a Raman study of several Ga 1-x In x P samples grown by atomic layer epitaxy. The Ga... more We report on a Raman study of several Ga 1-x In x P samples grown by atomic layer epitaxy. The Ga 1-x In x P LO-phonon Raman peaks are present in the z(xx)z¯ (polarized) spectrum as well as the z(xy)z¯ (depolarized) spectrum, in contradiction to the usual selection rules for ...
The potential applications of Atomic Layer Epitaxy of HI-V compounds will be outlined. These incl... more The potential applications of Atomic Layer Epitaxy of HI-V compounds will be outlined. These include the growth of special structures and devices such as ordered alloys, ultra-thin quantum wells, non-alloyed contacts, planar doped FET's and HBT's. Also, the main challenges facing ALE will be outlined along with possible solutions. These include reactor design, control of carbon doping and the growth of ternary alloys. A general assessment of the ALE technology will be provided.
Dilute Magnetic Semiconductor (DMS) research has mainly focused on II−VI and III−V materials, whe... more Dilute Magnetic Semiconductor (DMS) research has mainly focused on II−VI and III−V materials, where a maximum Curie temperature (T C) of 110K was reported in (Ga,Mn)As.[1] However, (Ga,Mn)N has shown ferromagnetic behavior with Curie temperature (T C) exceeding room temperature. [2] ,[3],[4] The elevated Curie temperatures exhibited in this material has obvious and practical technological implications. Efforts to grow (Ga,Mn)N by metal−organic chemical vapor deposition (MOCVD) have produced much information on the optical properties of the films. Korotkov[5] et al. shows that Mn forms a deep acceptor level with optical transitions at 1.4 and 2.06 eV, and photoluminescence measurements of Mn−doped films indicated the presence of an intra 3d−shell transition of the Mn ion. However, there were no reports on the magnetic properties or crystalline quality of this material system grown by MOCVD. The purpose of this study is to demonstrate room temperature ferromagnetic MOCVD grown (Ga,Mn)...
The principal objective of research conducted under this contract during the past twelve months h... more The principal objective of research conducted under this contract during the past twelve months has been the development and fabrication of two junction cascade solar cells in two different III-V semiconductor materials systems: AlGaAs/GaAs and AlGaAsSb/GaAsSb. Liquid phase epitaxy (LPE) has been successfully used to fabricate experimental cascade cells in both of these materials systems. Additional research has been carried out using organometallic/chemical vapor deposition (OM/CVD) growth technology.
2000 IEEE International Symposium on Compound Semiconductors. Proceedings of the IEEE Twenty-Seventh International Symposium on Compound Semiconductors (Cat. No.00TH8498), 2000
Six types of systematic photoluminescence (PL) surements (T ≥ 77 K) were carried out on single cr... more Six types of systematic photoluminescence (PL) surements (T ≥ 77 K) were carried out on single crystals of AlxGa1-xAs (x ~ 0.3) undoped or doped with Be by LPE or ion implantation. The multimea-surements approach was employed in order to ascertain that the highest-energy radiative recombination was in fact band-to-band (BTB), and consequently to obtain accurate activation energies. LPE doped
Cascade solar cells may now be the only promising approach to achieve high conversion efficiency;... more Cascade solar cells may now be the only promising approach to achieve high conversion efficiency; however, several technical problems have to be solved first. It is hoped that enough effort and time will be given to this structure so that an efficiency of over 30% can be achieved. Organometallic chemical vapor deposition seems to be the most suitable growth technique for this structure. Thus, it is suggested that current activities should be directed to solve problems associated with this technique.
ABSTRACTAtomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology h... more ABSTRACTAtomic layer epitaxy(ALE) of III-V compound semiconductors is reviewed. This technology has grown in recent years because of potential applications to nanometer-order structures as well as to monolayer/cycle growth with high-uniformity in growth thickness, and to excellent selective-area growth. Recent developments in chloride ALE of various compounds and heterostructures are described. Potentials of ALE for producing such fine structures are shown.
Abstract We report the first demonstration of an AlGaAs/GaAs resonant tunneling diode (RTD) grown... more Abstract We report the first demonstration of an AlGaAs/GaAs resonant tunneling diode (RTD) grown by atomic layer epitaxy (ALE) which features room temperature negative differential resistance. The ALE growth is obtained in a rotating susceptor system with trimethylgallium, trimethylaluminum and arsine sources. Wafer mapping of the RTD properties indicates that monolayer thickness control can be achieved by this technique. In addition to vertical resonant tunneling, we also describe the application of ALE to realize ...
Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high tem... more Residual surface contaminants were removed from vicinal 6H-SiC(0001) surfaces in UHV via high temperature annealing in SiH4. Characterization via AES, EELS, LEED, XPS, and UPS was conducted. At T greater than 850 C, the surface oxide was rapidly removed. Exposure to approx. 400 Langmuir (10(exp -6) Torr(dot)liter/s) of SiH4 resulted in complete surface oxide removal and a nearly stoichiometric (l x l) 6H-SiC surface suitable for ALE of SiC. Further exposure resulted in a (3 x 3)R30 deg Si-rich reconstructed surface. Subsequent annealing in UHV resulted in a (square root of 3 x square root of 3)R30 deg Si deficient/graphitic reconstructed surface. The first set of wafers containing HBT device structures were fabricated on SiC films grown via ALE. No transistor activity was detected. Electrical characterization and SEM showed the most likely fault to be inaccurate etching of the SiC emitter. Nucleation and growth of oriented diamond particles on seeded, group of zone axes (0001) orien...
Correlation between structural defects and appearance of multiple cathodoluminescence and photolu... more Correlation between structural defects and appearance of multiple cathodoluminescence and photoluminescence peaks of In x Ga 1-x N grown nominally with x=0.1 and increasing layer thickness (100 nm to 1000 nm) is discussed. Cathodoluminescence studies were performed on the cross-section samples earlier characterized by electron microscopy including Zcontrast microscopy. Strained and relaxed layers with different In concentrations were observed for InGaN layers above the critical layer thickness. Stacking faults appear at high density in the relaxed layer which also roughens, created a sawtooth surface profile due to V-shaped pits. Large domains of closely separated stacking faults (polytype-like) were observed. In Z-contrast microscopy stacking faults in upper/lower part of the layer appear with higher/lower brightness, suggesting different amount of In incorporation in agreement with x-ray and RBS results. Only thin, strained In-GaN layers showed single band-edge CL peaks. Multiple CL peaks appear in the relaxed, defective portion of the InGaN layers. By comparison with GaN samples where structural defects are associated with CL peak shifts, we postulate that defects, their type and distribution are main contributors to the multiple peaks observed for InGaN samples.
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
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