摘要:

We summarize the room‐temperature minority‐carrier mobility, minority‐carrier lifetime, and effective band‐gap shrinkage forp‐type GaAs at large dopings, as determined from measurements on heterostructure bipolar transistors and published literature. The minority‐carrier mobilities are significantly smaller than the majority‐carrier mobilities, the lifetime data show a change in dependence on doping at 1×1019cm−3, and the effective band‐gap shrinkage is ≊5% at 1×1019cm−3. The fits to electrical parameters described here should be of interest in modeling of minority‐carrier devices.

ISSN:0003-6951    

DOI:10.1063/1.102745

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Yb‐doped InP has been prepared by metalorganic vapor phase epitaxy using a Yb fluorinated beta‐diketonate. The doped layers werentype with carrier concentrations ranging from 0.6 to 17×1015cm−3. The doped layers exhibited the characteristic Yb+3‐4fphotoluminescent emission at 1.23 eV. The low‐temperature photoluminescence indicates the association of Yb with other centers to form complexes.

ISSN:0003-6951    

DOI:10.1063/1.102746

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We have used x‐ray photoelectron spectroscopy to measure the valence‐band offsetinsitufor strained Si/Ge (100) heterojunctions grown by molecular beam epitaxy. Si 2pand Ge 3dcore level to valence‐band‐edge binding energies and Si 2pto Ge 3dcore level energy separations were measured as functions of strain, and strain configurations in all samples were determined using x‐ray diffraction. Our measurements yield valence‐band offset values of 0.83±0.11 eV and 0.22±0.13 eV for Ge on Si (100) and Si on Ge (100), respectively. If we assume that the offset between the weighted averages of the light hole, heavy hole, and spin‐orbit valence bands in Si and Ge is independent of strain, we obtain a discontinuity in the average valence‐band edge of 0.49±0.13 eV.

ISSN:0003-6951    

DOI:10.1063/1.102747

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Experiments are described employing secondary‐ion mass spectroscopy (SIMS) to study the stability of13C‐doped Al0.5Ga0.5As‐GaAs superlattices against Zn and Si impurity‐induced layer disordering (IILD). The modulation depth of the SIMS27Al and13C signals is used as a sensitive probe of column III and column V sublattice interdiffusion. The data show that CAsis much more stable against Zn and Si IILD than the column III superlattice host crystal itself. The minor enhancement of CAsdiffusion via the column III disordering agents, which is present to a significant extent for Si IILD but almost nonexistent for Zn IILD, suggests that there is no direct interchange of column III and column V sublattice atoms. The Zn and Si enhancement of carbon diffusion is probably caused by local Coulombic interaction between the diffusing Zn+iand Si+IIIspecies and the C−Asacceptor.

ISSN:0003-6951    

DOI:10.1063/1.102748

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Thin films of the Bi2(Sr,Ca)3Cu2Oxand YBa2Cu3O7−&dgr;system were annealed at 400 °C in a high‐density oxygen plasma and its effect on superconducting properties was investigated. After being annealed in the oxygen plasma, their superconducting transition temperatures decreased by about 10 K and 2 K, respectively, and thec‐axis lattice constants of these films were also found to decrease as a result of the annealing in the oxygen plasma. These results suggest that excessive oxygen incorporated into the films by the annealing in the oxygen plasma caused the excessive hole carriers, which deteriorated the superconducting transition temperatures of these films.

ISSN:0003-6951    

DOI:10.1063/1.103302

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Broad angular distributions have been observed for XeCl laser ablation plumes used in the deposition of YBa2Cu3O7−&dgr;thin films. Distributions (inferred from film thickness) and film stoichiometry were measured as a function of laser fluence, beam shape, and oxygen pressure. Parallel to the long axis of the laser spot, plumes exhibited a cos3.5(&thgr;) spread and composition varied with angle; in the perpendicular direction, more diffuse [cos1.5(&thgr;)] plume distributions were associated with stoichiometric deposition. The observed phenomena are consistent with formation of a Knudsen layer near the target surface.

ISSN:0003-6951    

DOI:10.1063/1.103303

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using rf sputtering technique, thin films of near single phase Bi2Sr2Ca2Cu3Oxwere successfully prepared on SrTiO3(100), MgO(100), and LaAlO3(012) substrates. Zero resistance of these films occurred in the range of 90–105 K.

ISSN:0003-6951    

DOI:10.1063/1.103304

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The conversion of long slender filaments of Bi‐based high‐temperature superconductors from the amorphous to the crystalline phase has been studied in order to determine the suitability of these fibers for use in a multifilamentary magnet conductor. For very fine filaments, coarsening may be a problem, so special emphasis was placed on the optimum values of time and temperature used for recrystallization. Amorphous fibers approximately 1 &mgr;m in diameter can be crystallized to form granular filaments about 0.2 &mgr;m thick (in thecdirection) and 3 to 4 &mgr;m wide. Thecaxis generally grows perpendicular to the long axis of the fiber.

ISSN:0003-6951    

DOI:10.1063/1.103305

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using mechanical alloying and an additional annealing, we prepared bulk material of a new Sm20Fe70Ti10phase observed before only in sputtered films deposited in the amorphous state and then crystallized. Crystallization of rapidly quenched and partially amorphous ribbons leads to a two‐phase material with a considerable amount of this phase but with the Fe2Sm phase as a majority phase. This new phase (named 20:70:10 phase) has a Curie temperature of 380 °C and an estimated saturation magnetization of 6–7 kG. The magnetically isotropic, mechanically alloyed samples show room‐temperature coercivities of up to 50.3 kOe.

ISSN:0003-6951    

DOI:10.1063/1.103306

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Aqueous suspensions of elongated, hollow tubules are shown to align in magnetic fields of order 10 G when mixed with a water‐based ferrofluid. The tubule’s effective susceptibility anisotropy is obtained, and is found to be six orders of magnitude larger than in the absence of the ferrofluid. A geometry‐based model is used to explain this effect.

ISSN:0003-6951    

DOI:10.1063/1.102749

出版商:AIP    

年代:1990

数据来源: AIP