摘要:

The nature of dislocations in (001) CdTe‐(001) GaAs heterostructures was investigated by transmission electron microscopy. The samples were grown by metalorganic chemical vapor deposition with CdTe layer thicknesseshranging from 0.1 to 2.2 &mgr;m. The interface contains an array of misfit dislocations spaced about 31 A˚ apart, independent ofh. These dislocations do not relax all of the lattice mismatch (14.6%) in the CdTe layers withh<1 &mgr;m. Above the interfaces, surface nucleated dislocations are observed in the CdTe layers and their density depends onh. No evidence of an oxide or foreign interface layer was found in these samples.

ISSN:0003-6951    

DOI:10.1063/1.97842

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A method for producing high‐tilt boundary conditions for liquid crystals has been developed which requires only chemical treatment followed by conventional rubbing techniques. The basic concept involves two chemicals: one which, by itself, produces homogeneous orientation, and the other which, by itself, gives homeotropic orientation. By varying the relative concentrations of the two components, it is possible to balance the surface forces to give any desired tilt angle. The chemicals chosen were two silanes:N‐methylaminopropyltrimethoxysilane and octadecyltriethoxysilane, where the former is the homogeneous component and the latter is the homeotropic component. Although the system has some practical limitations, such as time‐dependent solution behavior and high‐temperature instability, it is possible to produce the entire range of tilt angles from homogeneous to homeotropic.

ISSN:0003-6951    

DOI:10.1063/1.97843

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The radiative recombination coefficientB, defined bydN/dt=dP/dt≡−BNP, of two‐dimensional free carriers,NandP, in a selectively doped GaAs/n‐Al0.3Ga0.7As quantum well was determined in the temperature rangeTbetween 15 and 300 K by measuring the decay time &tgr; of photoluminescence from the quantum well with electron densityN0=1×1012/cm2. It is found thatB(=1/&tgr;N0) is 1.1–1.9×10−4cm2/s at 300 K and increases asTis lowered, reaching 2.3×10−3cm2/s (&tgr;∼0.43 ns) at 15 K. The initial increase ofBis nearly proportional to 1/T, whereasBtends to saturate at low temperature. These experimental findings are shown to be well explained by the theory of band‐to‐band recombination of two‐dimensional carriers in quantum wells.

ISSN:0003-6951    

DOI:10.1063/1.97844

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The activation ratio of Fe atoms introduced in semi‐insulating (SI) InP layers grown by liquid phase epitaxy (LPE) and metalorganic chemical vapor deposition (MOCVD) has been investigated, employing the current‐voltage characteristics ofn+‐SI‐n+InP diodes and secondary ion mass spectroscopy analysis. The result indicates that most Fe atoms in LPE‐grown SI layers are electrically active as deep acceptors; however, a large amount of unactivated Fe atoms are present in MOCVD‐grown SI layers. This difference between the two kinds of Fe‐doped SI layers can be attributed to the difference in the growth mechanisms of LPE and MOCVD.

ISSN:0003-6951    

DOI:10.1063/1.97845

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Atomic layer doping ofp‐type carbon impurity in GaAs was demonstrated using flow‐rate modulation epitaxy. An extremely narrow capacitance‐voltage profile with 5.8 nm full width at half‐maximum is observed in the wafer with a sheet hole density of 9.5×1011cm−2. Atomic layer doping of carbon was performed by supplying trimethylgallium or trimethylaluminium instead of triethylgallium. It was found that the sheet hole density does not change before and after annealing for 1 h at 800 °C indicating that the carbon is a very stable impurity in GaAs. The diffusion coefficient of carbon is estimated to be 2×10−16cm−2/s at 800 °C. This is the lowest value ever reported forp‐type impurities.

ISSN:0003-6951    

DOI:10.1063/1.97846

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The Hall effect is used to measure the transient change in the carrier concentration in a semiconductor sample due to the thermal emission from states filled by a pulsed perturbation. This method has several advantages over other methods based on measuring the capacitance transient or the current transient. The identity of the released carriers can be determined from the sign of the Hall voltage. The new method is applied to the measurement of traps in epitaxial GaAs.

ISSN:0003-6951    

DOI:10.1063/1.97847

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The orientation of CdTe grown epitaxially onto clean (100) GaAs by molecular beam epitaxy can be predetermined by the GaAs precursor surface reconstruction that is present where the CdTe growth is initiated. A Ga‐stabilized GaAs starting surface yields CdTe (111) and an As‐stabilized GaAs surface yields CdTe (100).

ISSN:0003-6951    

DOI:10.1063/1.97848

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Rapid thermal annealing has been used to electrically activate Si‐implanted InP:Fe. A two‐step annealing cycle in which the short (5 s) high‐temperature step is followed by a relatively long (25–60 s) 100 °C lower temperature step gave higher activation and carrier mobility than the corresponding short high‐temperature or long low‐temperature single step annealing cycle. A good surface morphology was achieved by using InP proximity anneal if the maximum annealing temperature is limited to 900 °C for not more than 5 s. The maximum mobilities and activations obtained for 200 keV/5×1013cm−2and 150 keV/1×1013cm−2Si+implants were 1740 and 2260 cm2/V s and 88 and 98%, respectively. The position of the peak carrier concentration in the depth profile closely matched that of the Lindhard–Scharff–Schiott prediction.

ISSN:0003-6951    

DOI:10.1063/1.97849

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

In this letter we report for the first time the fabrication of bulk‐quality bipolar transistors in low‐temperature (Tdep=800 °C) epitaxial silicon. The epitaxial layers were deposited by an ultra‐low pressure chemical vapor deposition technique utilizing aninsitupredeposition argon sputter clean. The critical parameter affecting the quality of the epitaxial films is the deposition temperature. The junction leakage current decreases by two orders of magnitude, the ideality factor improves from 1.36 to 1.04, and the minority‐carrier lifetime increases from 1.3 to 46 &mgr;s as the deposition temperature is increased from 750 to 800 °C. Analysis of the base‐emitter and base‐collector junction characteristics indicates that bipolar transistors fabricated in epitaxial films deposited at 800 °C have characteristicsatleastas good as control fabricated in bulk silicon.

ISSN:0003-6951    

DOI:10.1063/1.97850

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Electron spin resonance measurements of silicon‐on‐insulator materials formed oxygen implantation are reported. The principal paramagnetic defect observed is aPbcenter at the interface between Si and SiO2precipitates in the Si film over the buried oxide layer. The29Si central hyperfine interaction and the29Si superhyperfine interaction with neighboring Si atoms are resolved. The results are very close to those for thePbcenter at the Si‐thermal oxide interface and recent theoretical calculations.

ISSN:0003-6951    

DOI:10.1063/1.97798

出版商:AIP    

年代:1987

数据来源: AIP