摘要:

Admittance spectroscopy and deep-level transient spectroscopy measurements have been performed onn+-on-pHg1−xCdxTe(x=0.595)planar photodiodes grown by improved zone melt method. After 1.0 Mrads gamma irradiation, a new trap center is observed at 0.19 eV above the valence band, while the well-known 0.15 eV trap level disappears. The trap densities for these two levels are almost the same. We attribute this phenomenon to the gamma irradiation, which produces a compound defect correlated with Hg vacancy. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121790

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We provide direct evidence that Er ions incorporated in the depletion layer of ap+–n+Si junction are efficiently pumped through an impact excitation process with hot carriers. The carriers were accelerated by the electric field present in the depletion layer after being produced by either Zener breakdown of the junction at ∼5 V or by irradiating the diode with an argon laser. Measurements of the electroluminescence yield at 1.54 &mgr;m as a function of the reverse bias voltage (and for a constant current through the device) reveal that excitation of Er only occurs at voltages above 1 V, demonstrating that impact is the pumping mechanism. Moreover, we have found that Er ions are only excited within ∼15 nm from the edges of the depletion layer leaving a dark, ∼50 nm thick, region in the central part of the depletion region. Monte Carlo calculations confirmed that only close to the depletion layer edges the energy gained by the carriers in the electric field is high enough to impact excite Er. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121791

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present cross-sectional scanning tunneling microscopy images and scanning tunneling spectroscopy results of InAs quantum dots grown on GaAs. The samples contain 12 arrays of quantum dots. The analysis of the scanning tunneling microscope images reveals the self-alignment of the dots as well as the different dot interfaces with the under- and overgrown GaAs layers. We measure the strain distribution along the [001] direction in the (110) plane. The roughness of the dot interfaces along the [1¯10] direction is also estimated and local spectroscopy of the dots evidences the electronic confinement (measured gap of 1.25 eV compared with 0.4 eV for bulk InAs). ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121792

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In this letter, we examine the feasibility of applying positron annihilation spectroscopy to the study of hydrogenized amorphous silicon(a-Si:H)-based structures produced by chemical vapor deposition techniques. The positron probe, sensitive to open volume formations, is used to characterize neutral and negatively charged silicon dangling bonds, typical for undoped andn-dopeda-Si:H,respectively. Using depth profiling along the growth direction a difference was observed in the electronic environment of these defects, which enables their identification in ap-i-ndevice. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121793

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Room temperature continuous wave operation of ZnSe-based blue/green laser diodes grown homoepitaxially on conductive ZnSe substrates with threshold current densities as low as176 A/cm2has been demonstrated. This is the lowest reported threshold among all short wavelength lasers in the blue/green region. Lifetimes at room temperature of up to 2.1 h have been obtained for lasers with pre-existing defect densities lower than3×104 cm−2.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121781

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A thin layer of plasma enhanced chemical vapor deposited (PECVD) heavily phosphorus doped hydrogenated amorphous silicon(a-Si:H)film was annealed by cwAr+laser scanning. Different from conventionally prepared polycrystalline Si films, it was found that nanocrystalline Si (nc-Si) was formed in our laser annealed sample. Room-temperature green electroluminescence (EL) peaked at 530 nm was achieved from our nc-Si film. Photoluminescence (PL) from the same sample also shows the 530 nm green peak, in addition to the red peak located at 680 nm. The film had a rather high electrical conductivity of 10S/cm as well. The light emitting and highly conductive nc-Si film provides a new possibility to fabricate optoelectronic devices along with the well-developed laser annealing techniques ofa-Si:H.©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121782

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A technology has been developed to make all polymer integrated circuits. It involves reproducible fabrication of field-effect transistors in which the semiconducting, conducting and insulating parts are all made of polymers. The fabrication on flexible substrates uses spin-coating of electrically active precursors and patternwise exposure of the deposited films. In the whole process stack integrity is maintained. Vertical interconnects are made mechanically. As a demonstrator functional 15-bit programmable code generators are fabricated. These circuits still operate when the foils are sharply bent. Due to the limited number of process steps the technology is potentially inexpensive. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121783

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Measurements of the frequency dependence of the complex admittance are used to separate the ionic and electronic contributions in polymer light-emitting electrochemical cells (LECs). At zero bias, a large polarizability, attributed to salt molecules in the electrolyte, is observed at low frequencies. Ions are generated when the LEC is biased at voltages above the threshold for electrochemical redox doping. Because of the slow ionic response, a novel pulsed drive scheme is proposed: the mean value stabilizes the inducedp-i-njunction, while the peak value controls the carrier injection and the brightness of the electroluminescent emission. LECs operated in this way exhibit fast emissive response and improved operating life. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121784

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Photoreflectance has been used to study the electronic properties of (100) GaAs surfaces exposed to aCl2/Arplasma generated by an electron cyclotron resonance source and subsequently passivated byP2S5.The plasma etch shifts the Fermi level ofp-GaAsfrom near the valence band to midgap, but has no effect onn-GaAs.For ion energies below 250 eV, post-etchP2S5chemical passivation removes the surface etch damage and restores the electronic properties to pre-etch conditions. Above 250 eV, the etch produces subsurface defects which cannot be chemically passivated. Auger electron spectroscopy shows that etching increases As at the GaAs/oxide interface, while passivation reduces it. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121785

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Artificial bulk “zero-angle” boundaries parallel to thecaxis have been engineered between large melt-processedYBa2Cu3O7−&dgr;(YBCO) grains and observed to carry a transport supercurrent at fields up to at least 5 T at 77 K. The temperature and angular dependencies of the boundary resistance have exactly the same form as those of the grains, which is evidence that the grains are intimately coupled. The limiting mechanism for current transfer across these boundaries is, therefore, not a simple weak link or Josephson effect. This joining technique is extremely promising for production of macroscopic engineering artifacts. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121786

出版商:AIP    

年代:1998

数据来源: AIP