摘要:

Results are reported on the Zintl phase material, K4In4Sb6, with respect to laser ablation and subsequent laser ionization/removal processes. A 308 nm laser pulse is used to ablate the Zintl compound, while a second laser ionizes ejected species within the extraction region of a time‐of‐flight mass spectrometer. With the second laser operating at 248 nm, selective ionization and removal of the potassium is clearly demonstrated. Such a strategy takes advantage of the different ionization potentials of K, In, and Sb, and implications for possible applications of this research to film growth are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113179

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The oxidation of amorphous Si0.65Ge0.27C0.08and single‐crystal Si0.63Ge0.36C0.01in wet ambient at 700 and 900 °C has been studied using Rutherford backscattering spectrometry and transmission electron microscopy. A reference sample of Si0.63Ge0.37was also oxidized in order to determine the influence of carbon on the oxidation behavior. The low C content alloy behaved similar to the SiGe alloy: uniform Si1‐xGexO2was obtained at 700 °C whereas SiO2was formed at 900 °C, and Ge piled up underneath the oxide. In both cases, carbon was not detected in the oxide layer. The amorphous Si0.65Ge0.27C0.08alloy behaved significantly different at both oxidation temperatures in comparison with the crystalline Si0.63Ge0.36C0.01and Si0.65Ge0.37. Negligible oxidation occurred at 700 °C whereas SiO2was obtained at 900 °C and the rejected Ge distributed uniformly throughout the SiGeC alloy. It is proposed that fast Ge diffusion during oxidation at 900 °C resulted from diffusion at grain boundaries, since crystallization of the amorphous SiGeC layer occurred in conjunction with oxidation, leading to nucleation of nanocrystals (∼5 nm diam). The oxidation/annealing treatment has thus provided a useful mechanism for increasing the relative Ge concentration in the SiGeC alloy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113180

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A large‐angle convergent‐beam electron diffraction (LACBED) pattern with fine diffraction lines from a cross‐sectional specimen of GexSi1−x/Si strained‐layer superlattices (SLS) can give much information on local strain and misfit stress relaxation. The shift of the diffraction lines in the GeSi layers from those in the Si layers can be used to determine the strain relaxation. A profile of the thin film relaxation versus the specimen thickness is presented. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113181

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A detailed investigation of the dependence of the photoluminescence from porous silicon carbide on preparation conditions and starting material is presented. Porous silicon carbide prepared from different polytypes shows almost identical emission spectra, demonstrating a clear impedance of the band‐gap energy of a particular SiC polytype. Emission bands with peak energies of 2.43, 2.22, 2.07, and 1.93 eV were resolved with the use of selective excitation by tuning the excitation wavelength. The origin of luminescence is suggested to relate to defect states produced at the etched surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113182

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Indium segregation in InxGa1−xAs/GaAs (0.05<x<0.25) quantum wells grown by molecular beam epitaxy has been investigated using low temperature photoluminescence. Additional features at low energy are evident in some of the spectra that are consistent with trapping of free excitons by In‐rich islands at the top interface, which occurs as the result of In segregation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113183

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A resonant electron irradiation‐induced deep level SE0 in GaAs layers has been investigated by using 50–50 A˚ uniformly Si‐doped GaAs‐Ga0.7Al0.3As superlattices and characterized by deep level transient spectroscopy. The formation of a miniband in superlattices changes the forbidden band gap and allows some resonant defects in bulk materials such as SE0 in GaAs to be detected. In these superlattices, three electron irradiation induced deep levels SE0, SE1, and SE2 located in GaAs layers have been observed. In bulk GaAs only two levels, E1 and E2, corresponding to SE1 and SE2 can be detected, since SE0 is a resonant level in bulk GaAs, situated 60 meV above the GaAs conduction band edge. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113184

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A noninvasive, photoconductive sampling technique, which does not require short‐lifetime material to achieve picosecond temporal resolution, is demonstrated. The technique relies on electromagnetic coupling to generate the time derivative of the signal of interest in a separate sampling circuit. A slow photoconductive device in the sampling circuit integrates the coupled signal to produce the desired wave form. A 5‐ps sampling response (limited only by circuit parasitics) was measured on GaAs with a lifetime of 1 ns by coupling to a small conducting loop. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113185

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A detailed theoretical investigation of dark current mechanisms is performed for a novel Sin+‐ihomojunction interfacial work function internal photoemission (HIWIP) far‐infrared (FIR) detector. Thermionic emission, thermionic field emission and field emission currents, including the image force effect, are calculated and compared as functions of bias voltage and temperature. The bias and temperature dependence of detector noise equivalent power (NEP), limited by thermal noise and background noise, is also calculated. From these results, the optimal operating temperatures and bias voltages are determined. Results show that Si HIWIP FIR detectors may have a performance comparable to the conventional Ge FIR detectors, with some unique advantages over them. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113186

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using cross‐section and plan‐view transmission electron microscopy we demonstrate that the initial plastic relaxation of highly mismatched layers grown along [100] is governed by the growth mode. During MBE growth of InAs on GaAs in the Stranski‐Krastanov (SK) mode, 60o ‐type dislocations are generated at the island edges and then glide to the interface to relieve the strain. The resulting interfacial microstructure consists of an inefficient arrangement of misfit dislocations. On the other hand, when InAs is forced to grow in a two‐dimensional (2D) mode, only pure edge‐type dislocations are generated and they are located exactly at the epilayer/substrate interfacial plane. These results are explained by a different dislocation nucleation mechanism imposed by the planar morphology of the highly strained film. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113187

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The observation of light hole intersubband absorption in bothp‐doped and photoexcited undoped strained InxGa1−xAs/InP (x&bartil;0.35) quantum‐well structures is reported. The absorption is polarized along the growth direction and is in agreement with calculations which show that the strain causes the light hole level to be first occupied uponp‐doping or photoexcitation. Both impurity bound and free holes transitions are identified. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113188

出版商:AIP    

年代:1995

数据来源: AIP