摘要:

We report on a new method for the generation of phosphorus beams in molecular beam epitaxy: the use of a valved, solid cracker source. The valved solid source avoids previous difficulties associated with the use of solid phosphorus, and provides an attractive alternative to the use of phosphine. The use of red phosphorus does not interfere with the subsequent growth of high quality arsenides in the same growth chamber. The performance of this valved phosphorus source is illustrated by the growth of two ternary phosphides, Ga0.5In0.5P and Al0.5In0.5P. The quality of the phosphides reported here is comparable to the best results reported by other growth techniques. The effects of composition, growth temperature, and P2flux on the films’ characteristics are reported. Indium desorption during growth is found to be substantially greater in AlInP than in GaInP.

ISSN:0003-6951    

DOI:10.1063/1.105590

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We demonstrate that for the same capacitance value, 9.5‐nm‐thick oxide‐nitride storage dielectrics deposited on rough polycrystalline silicon exhibit a lower leakage current and a higher lifetime than 5.9 nm layers on smooth polycrystalline silicon. Leakage current reduction of more than two orders of magnitude and a lifetime increase of more than three orders of magnitude are reported. These improvements are explained by the nitride bulk‐limited type of conduction. Our data show that textured storage capacitors have all the properties required for efficient fabrication of 64 megabit dynamic random access memories.

ISSN:0003-6951    

DOI:10.1063/1.105591

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Sub‐100 nmP+/Njunctions were fabricated using plasma immersion ion implantation (PIII). With this technique, the silicon wafer was immersed in SiF4/BF3plasma and biased with a negative voltage. The positively charged ions in the plasma sheath were accelerated by the electric field and implanted into the wafer. The dose rate of PIII can be much higher than that of conventional ion implanter. Whereas the dopant activation behavior is similar. For extremely shallowP+/Njunction formation, sample preamorphization and short cycle rapid thermal annealing (RTA) are required. With SiF4PIII preamorphization followed by BF3PIII doping and RTA at 1060 °C for 1 s, 80 nmP+/Njunctions were successfully obtained. Test diodes fabricated with this technique show good characteristics.

ISSN:0003-6951    

DOI:10.1063/1.106392

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Time‐resolved photoluminescence of phonon‐assisted stimulated emission is reported for the first time. The temporal characteristics of the phonon‐assisted stimulated emission are distinct from the stimulated emission from the quantum states. The phonon‐assisted recombination is always delayed in time with respect to the confined particle transitions and has a larger full width at half maximum than the confined particle transitions. The dynamics of stimulated phonon emission along with the smaller transition probability for the phonon‐assisted process may account for the distinct temporal characteristics. Data are presented on the emission intensity versus wavelength versus time from which the dependence of the delay on excitation intensity is extracted.

ISSN:0003-6951    

DOI:10.1063/1.105592

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Data are presented demonstrating the formation of stable, device‐quality native oxides from high Al composition In0.5(AlxGa1−x)0.5P (x∼0.9) via reaction with H2O vapor (in N2carrier gas) at elevated temperatures (≥500 °C). The oxide exhibits excellent current‐blocking characteristics and is employed to fabricate continuous room‐temperature stripe‐geometry In0.5(AlxGa1−x)0.5P‐In0.5Ga0.5P double‐heterostructure laser diodes.

ISSN:0003-6951    

DOI:10.1063/1.105593

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Superconducting YBa2Cu3O7−&dgr;(YBCO) thin films have been depositedinsituon GaAs(100) by laser evaporation using yttria‐stabilized zirconia (YSZ) as a buffer layer. The YSZ buffer layer was deposited at room temperature initially, followed by a deposition at 650 °C. The YBCO layers were deposited subsequently at substrate temperature of 650 °C. All the depositions were carried out in a single chamber equipped with a multitarget holder using KrF excimer laser, &lgr;=248 nm. The morphology and structure of the buffer layer and YBCO films were determined using x‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and Auger spectroscopy. The nature of YSZ films was determined to be polycrystalline with partial texturing. The YBCO superconducting thin films on these YSZ‐coated GaAs specimens exhibited strong (00l) orientation with peak intensities similar to those observed on single‐crystal YSZ substrates. The superconducting transition temperatureTc(onset) of 92 K andTc0(zero resistance) of 73 K were achieved for YBCO thin films on GaAs with YSZ buffer layers.

ISSN:0003-6951    

DOI:10.1063/1.105594

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Measurements of the dctransportcritical current of oriented‐grained YBa2Cu3O7have been made using high quality Ag contacts and a high‐current sample mount. The critical‐ current densityJcat 77 K for mutually perpendicular current and magnetic field B in thea,bplane is 8 kA/cm2at 8 T, decreasing gradually to 3.7 kA/cm2at 20 T, and remaining over 1 kA/cm2out to 30 T. High magnetic field measurements ofJcas a function of the angle &thgr; of B with respect to thecaxis are also reported. In contrast to earlier results at lower fields (<3 T) the measurements reported here in high fields reveal aJcvs &thgr; curve with ahead‐and‐shouldersshape, consisting of a sharp peak (‘‘head’’) <5° wide for B parallel to the CuO2planes, and a wide (30° at 9 T, for example) shoulder region on either side ofB⊥c, where the transportJcremains high and constant. Beyond the shoulder region, however, the transportJcdecreases sharply, giving rise to the concept of acriticalfieldanglefor application design, defined by the minima ind2Jc/d&thgr;2at the edge of the shoulders.

ISSN:0003-6951    

DOI:10.1063/1.105595

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The first photoelectron spectroscopy results are presented for Ga and As growth on EuBa2Cu3O7−y(001) (EBCO) surfaces. Growth models are shown that explain these results. In Ga growth, the oxide state Ga initially covers the EBCO surface and then metallic state Ga grows on this surface as islands. On the other hand, As grows only one monolayer as the As oxide form without breaking CuO bonds at the As‐EBCO interface, implying that it may be possible to grow GaAs films on EBCO with the As‐oxide interlayer.

ISSN:0003-6951    

DOI:10.1063/1.105596

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The field dependence ofJcin partial‐melt‐processed Bi1.6Pb0.3Sb0.1Sr2Ca2Cu3Oxhas been investigated. The samples have a dense, polycrystalline microstructure of the (2223) phase with no significant crystallographic texture, and exhibitTc(&khgr;)∼105 K and transportJc(H=0)∼104A/cm2at 4.2 K. In high magnetic fields (e.g.,H=5 T), the transportJcis somewhat reduced but is still of substantial value. While the high‐angle grain boundaries in the present, partial‐melt‐processed samples are by no means weakly coupled, the field dependence of the critical current density [Jc(0)/Jc(5 T)∼10] is somewhat stronger than inc‐axis textured samples [Jc(0)/Jc(5 T)∼3]. The grain boundaries in the present polycrystalline samples may thus be viewed, on the average, as ‘‘mild’’ weak links. These results clearly indicate the necessity for grain texturing if the fullJccapability of the BSCCO‐type superconductors is to be exploited.

ISSN:0003-6951    

DOI:10.1063/1.105597

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Minimum energy states of a rather general domain wall are determined by a set of differential equations. By using these equations, the energy of any of those states is shown to be equal to the value given by an expression that contains second derivatives, and is, therefore, very sensitive to the wall structure. The closeness of the two values can thus be taken as a measure of the closeness of the computed structure to the real energy minimum. This is a generalization of a criterion that has only been used before for 180° walls. Several other cases are treated in detail, and for the particular case of 90° walls, numerical values are given for some published wall structures.

ISSN:0003-6951    

DOI:10.1063/1.105598

出版商:AIP    

年代:1991

数据来源: AIP