摘要:

The boron‐induced ( 7/8 × 7/8 )R30° reconstruction at the Si interface has been investigated by grazing incidence x‐ray diffraction. The in‐plane projected struture is found from the structure factors near zero perpendicular momentum transfer. At thea‐Si/Si (111) interface, boron atoms at 1/3 ML are substituted for silicon atoms, thus forming a ( 7/8 × 7/8 )R30° lattice and the boronsilicon bond is contracted compared with the siliconsilicon bond. Even at the interface between a solid phase epitaxial Si (111) layer and a Si (111) substrate, the boron‐induced ( 7/8 × 7/8 )R30° reconstruction has also been observed and the structure is similar to that observed at thea‐Si/Si (111) interface.

ISSN:0003-6951    

DOI:10.1063/1.102522

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We describe a method based on nuclear reaction analysis, using the reaction2H(3He,4He)1H, (Q=18.352 MeV) to determine composition profiles of deuterated polymer chains in thin films. By detecting the emitted &agr; particles (4He) at forward angles (30°) we are able to achieve a spatial resolution of 7 nm half width at half maximum (HWHM) at the deuterated sample surface, and 15 nm HWHM at a depth of some 130 nm. We use our method to probe initial diffusional broadening at the interface between deuterated and protonated polystyrene films. Our measured profiles are in close agreement with earlier measurements (over larger spatial scales) and with mean field models for the diffusional process in this system.

ISSN:0003-6951    

DOI:10.1063/1.103332

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We optimized Ge+and Si+preimplantation to eliminate the channeling tail and prevent the rapid diffusion of boron and the formation of serious defects. We examined the dependence of the microchanneling of BF+2implantation or the lattice disorder of preimplanted silicon using secondary‐ion mass spectroscopy and grazing exit Rutherford backscattering spectroscopy. The optimum doses are about 25% those for full amorphization, i.e., preamorphization. The channeling tail is eliminated by disordered layers containing about 60% silicon atoms on irregular sites.

ISSN:0003-6951    

DOI:10.1063/1.102523

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report on spectroscopic experimental evidence of type II band alignment in a (GaAs)6/(AlAs)6superlattice grown by molecular beam epitaxy along the (111) direction. This result is in contrast to recent theoretical calculations predicting that the (GaAs)n/(AlAs)nsuperlattices grown along the (111) direction should be direct for alln’s.

ISSN:0003-6951    

DOI:10.1063/1.103333

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Scanning transmission ion microscopy (STIM) has been used, in conjunction with channeling, to explore transmission channeling in 50‐&mgr;m‐thick epitaxially grownn‐type silicon with 3.9 MeV H+beam currents of 0.1 fA focused to spot sizes of less than 200 nm. The technique is extremely efficient, causes negligible damage, and is capable of very high resolution. High‐resolution images of crystal damage were obtained with this first demonstration of channeling contrast in STIM.

ISSN:0003-6951    

DOI:10.1063/1.102524

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using subpicosecond time‐resolved luminescence spectroscopy, we show that the tunneling rate for electrons in an asymmetric double quantum well structure changes dramatically as the energy separation between the two lowest conduction subbands of the coupled well system is tuned through the optical phonon energy. We model these experiments using an ensemble Monte Carlo simulation and obtain a good quantitative agreement between the two. These results demonstrate the importance of phonon‐assisted tunneling processes and raise a number of interesting questions concerning the nature of phonons and carrier‐phonon interactions in these structures.

ISSN:0003-6951    

DOI:10.1063/1.102525

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Epitaxial films of AlAs0.16Sb0.84and Al0.8Ga0.2As0.14Sb0.86were grown lattice matched on (100) InAs substrates by molecular beam epitaxy. The material was characterized by x‐ray diffraction, 4 K photoluminescence, and capacitance‐voltage measurement techniques. At 300 K, background acceptor concentrations of 1.8×1015and 1.4×1016cm−3were determined for the unintentionally doped AlAsSb and AlGaAsSb epitaxial layers, respectively. Compensating the AlAsSb and AlGaAsSb epitaxial layers with sulfur doping resulted in high‐resistivity material with an effective donor concentration of about 1014and 1015cm−3, respectively.

ISSN:0003-6951    

DOI:10.1063/1.102526

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using telegraph noise measurements on smalln‐ andp‐channel metal‐oxide‐silicon field‐effect transistors, we have measured the entropy change associated with the change of the charge state of individual slow Si/SiO2surface states. Inn‐channel devices we find that the entropy change is positive on electron emission to the silicon conduction band, while inp‐channel devices it is positive on hole emission to the valence band. The results suggest that the slow states in the upper and lower regions of the silicon band gap are of a different type.

ISSN:0003-6951    

DOI:10.1063/1.102527

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Heavily carbon‐doped GaAs was obtained by low‐pressure metalorganic chemical vapor deposition by using trimethylgallium and arsine with a low V/III ratio. The hole concentration became as high as 2×1019cm−3without using intentional doping source gases when the V/III ratio was decreased to 2.4. The hole concentration coincided with the carbon concentration measured by secondary‐ion mass spectroscopy. The epilayer surface tended to be rough when the V/III ratio was decreased below 10. However, when the V/III ratio was lowered to 2.4, the epilayer surface became completely mirror‐like.

ISSN:0003-6951    

DOI:10.1063/1.103181

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The redistribution of Zn in the base region of GaAs‐AlGaAs heterojunction bipolar transistor structures during growth by organometallic vapor phase epitaxy has been examined with respect to the presence of Si doping in the emitter‐contact, emitter, and collector/subcollector layers, and as a function of Zn doping concentration and Si counterdoping level in thep+base. For a growth temperature of 675 °C the Zn shows no significant redistribution up to concentrations of 3×1019cm−3without Si doping. The addition of Si to the adjacent AlGaAs emitter and collector/subcollector layers causes substantial diffusion of Zn from the base, while Si doping of the GaAs emitter contact results in even greater Zn redistribution. Under these conditions, the Zn concentration in the base attains a maximum value of ∼7×1018cm−3. Silicon counterdoping in the base region retards the Zn diffusion, while strain introduced by an InGaAs cap layer has no effect on the Zn redistribution.

ISSN:0003-6951    

DOI:10.1063/1.102528

出版商:AIP    

年代:1990

数据来源: AIP