摘要:

We have measured the electron and hole impact ionization coefficients in Si1−xGexalloys. Carrier multiplication measurements were made on relaxed Si1−xGex/Si diodes grown by gas source molecular beam epitaxy. The hole to electron impact ionization coefficient ratio, &bgr;/&agr;, varies from 0.3 to 4 in the composition range ofx=0.08–1.0. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113134

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The spatial collection efficiencyC(z) is the probability that a photon absorbed at the pointzin the cell will yield a charge carrier into the current. TheCfunction is obtained from the spectral response by means of the inverse Laplace transformation. It gives important information on the cell parameters such as diffusion length, junction depth, surface recombination velocity, etc. Examples ofc‐Si and thin‐film CdS/CdTe cells are given. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113135

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have estimated the valence band discontinuity &Dgr;EVat thep‐ZnSe/p‐ZnTe interface by means of electrical measurements. From capacitance‐voltage measurement of a Schottky‐like barrier at the heterojunction, &Dgr;EV∼0.8 eV is found. The current‐voltage characteristics of the junctions, however, suggest smaller values for &Dgr;EV. The likely origin of this difference is leakage paths of the current in the barrier at the junction. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113136

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

InAlAs/InGaAs high electron mobility transistors (HEMT) with excellent high frequency performance were demonstrated. Device sizes of 0.25×50 &mgr;m and 0.10×50 &mgr;m showed current gain cutoff frequencies of 143 and 205 GHz, respectively. The HEMT structures were grown on a low temperature InAlAs buffer layers designed to eliminate conductive impurity spikes situated at the epitaxial/substrate interface. The highly resistive buffer layer (2×105&OHgr; cm) was obtained at a growth temperature of 475 °C using a combination of trimethylarsenic and arsine as the arsenic sources. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113137

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The cathodoluminescence (CL) from porous silicon and thermal‐oxidized porous silicon was examined by x‐ray spectroscopy and photoluminescence (PL). Two dominant CL bands were observed at 460 nm (2.7 eV) and 650 nm (1.9 eV), respectively, which were not found in the PL spectrum. Electron beam irradiation caused degradation and/or increase in luminescence, and the two bands showed different variations. It has been concluded that electron beam excitation mainly occurs in amorphous SiO2, and the two bands are caused from different defects in amorphous SiO2covering the porous silicon. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113138

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

N‐doped vertical AlGaAs quantum wells have been fabricated by metalorganic vapor phase epitaxial growth of a single‐doped AlGaAs layer on a submicron grating. Intersubband absorption at normal incidence is demonstrated in those quantum wells. This opens new possibilities for infrared quantum well devices using intersubband transitions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113139

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Ferroelectric SrBi2Ta2O9thin films were synthesized on Pt/Ti/SiO2/Si substrates using a solution deposition process, and structural and electrical properties were investigated. The spin‐on films crystallized during firing above 700 °C. The films showed high diffraction peaks of (105) and (200), while little peaks from (00l) planes were observed. Good ferroelectric properties were obtained for a 280 nm thick film;PrandEcwere 10.0 &mgr;C/cm2and 38 kV/cm, respectively. Fatigue endurance was excellent; the hysteresis loop does not change up to 109switching cycles. These properties are very attractive for nonvolatile memory application. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113140

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Scanning tunneling microscopy is demonstrated for determining the surface morphology of etched Hg‐based semiconductors. Wet etching of HgTe/CdTe superlattices used a Br‐based etch solution while dry etching used methyl‐free radicals formed by electron cyclotron resonance in a reactive ion etching reactor. Both techniques produced smooth surfaces with random features over large regions. Features ranged in height from 1 to 5 nm for wet etching, while the smoothest dry etched sample had random features with an average height of 40 nm. Near mesa structures, evidence of differential etching was observed between the different composition layers in the HgTe/CdTe superlattices for both wet and dry etched samples. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113141

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigated the exciton dynamics in InGaAs/InP quantum wells using a novel infrared tunable femtosecond laser source, based on an optical parametric frequency converter pumped by a femtosecond Ti:sapphire laser. The wide tuning range of this source allowed to excite three different excitonic resonances in the absorption spectrum of the sample. Then=1 heavy‐hole excitons are approximately eight times more efficient than free electron‐hole plasma in the absorption saturation. This value is much higher than that measured in GaAs quantum wells. The exciton ionization time constant of then=1 andn=2 heavy‐hole excitons has been measured to be 170 and 100 fs, respectively. No evidence of then=1 light‐hole exciton dynamics was found in the measurements. The study of the dynamics at then=2 heavy‐hole resonance allowed the measurement of an=2 ton=1 intersubband relaxation time of 1 ps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113554

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have fabricated and tested picovoltmeters in which the voltage source is connected in series with a calibrated resistor and a coil inductively coupled to a high‐transition temperature superconducting quantum interference device operating at 77 K. The coil consists of either seven or ten turns of copper wire or of two turns patterned in a film of YBa2Cu3O7−x(YBCO). The lowest voltage noise achieved at 1 Hz was 30 pV Hz−1/2and 2.3 pV Hz−1/2for input coils made of copper and YBCO, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113555

出版商:AIP    

年代:1995

数据来源: AIP