摘要:

Three‐photon photoemission effect on GaAs–O–Cs negative electron affinity surfaces (NEA) was studied by using a nanosecond pulsed laser at 2.06 &mgr;m wavelength. The photocurrent densities from the photocathodes with different sensitivities were measured as a function of laser intensity at both room and liquid nitrogen temperatures (77 K). The dependence of photocurrent density on the light intensity shows a typical slope of three in logarithmic plot. The results are interpreted in terms of multiphoton photoemission (MPPE) effect. The influence of thermal electron emission to MPPE are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115518

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

GaN single crystal films were grown by atomic layer epitaxy at 550 °C. The room temperature photoluminescence properties of these low‐temperature‐grown films are dominated by band edge emission with intensity comparable to those grown by metalorganic chemical vapor deposition at 1000 °C. The as‐grown films have background‐carrier concentrations that can be controlled to levels in the 1016/cm−3range. Atomic layer epitaxy is therefore a good approach to the low temperature growth of nitride compounds. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115519

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Initial stage of InAs pseudomorphic layer transformation (1–3 ML) on GaAs (100) singular surface may result for sequential submonolayer molecular beam epitaxy in formation of a pseudoperiodic array of InAs ‘‘wires’’ along the [001] direction. Complex parquet structures having similar anisotropy are formed on misoriented surface (3° towards [0–11] direction). Increase in growth interruption time after each growth cycle for 2 ML InAs deposited on singular surface results in decomposition of the wires into dots arranged in a 2D square lattice. Intentional substrate misorientation stabilizes the initial ordering effect along [001] and does not change the direction of anisotropy. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115520

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrical conductivity, the thermoelectric power, and the electrical contribution to the thermal conductivity of quantum wire superlattices have been studied. The effects of tunneling through the barriers due to finite potential off‐sets and of the thermal currents through the barrier layers are shown to be essential to describe properly the thermoelectric figure of merit of realistic quantum wire superlattices. The figure of merit exhibits a maximum as a function of superlattice period which, for large barrier off‐sets, is found to be substantially enhanced over that for the bulk material and also larger than that for quantum well superlattices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115495

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We investigate by temperature‐dependent photoluminescence (PL) spectroscopy between 9 K and 300 K Zn1−xCdxSe/ZnSe strained‐layer quantum wells (QWs) with Cd contents ranging between 12% and 19% and QW thicknesses between 9 and 175 A˚, i.e., with confinement energies up to 220 meV. In the whole temperature range the PL spectra are dominated by E1‐HH1 free‐exciton recombinations. Between 9 and 300 K the intensity of this line is reduced by three to four orders of magnitude while transitions involving excited states progressively emerge. An analysis of the thermal quenching of the PL intensity reveals that for all confinement energies the escape of excitons out of the QWs is the mechanism responsible for this quenching near 300 K. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115496

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the investigation of the room‐temperature optoelectronic behavior of a metal–semiconductor–metal two‐dimensional electron gas photodiode based on the two‐dimensional electron gas of a high electron mobility transistor structure. The photodetector is fabricated in the InP/InGaAs material system, without use of Al‐containing layers. Optoelectronic measurements on a device with a finger spacing of 3 &mgr;m show a full width at half‐maximum (FWHM) of the pulse response of ≤60 ps, which is the resolution limit of our measurement equipment. Low‐temperature measurements at 40 K with electro‐optical sampling at a wavelength of 890 nm show a FWHM of 1 ps. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115497

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We show that small structures can be defined in high mobility two‐dimensional electron gases formed at a depth of 2770 A˚ below the surface in GaAs/Al0.33Ga0.67As heterostructures. The differential conductance of one‐dimensional constrictions defined by split gates in such deep electron gases showed more than 20 quantised plateaus. The absence of resonant structures on the plateaus demonstrates the absence of potential fluctuations in the constrictions. By applying a dc source‐drain bias we have measured the energy spacings of the first 18 subbands, and the effect of a small perpendicular magnetic field on the energy spacings has been investigated. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115498

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electrical properties and microstructures of Au/Pt/Ti/Ni ohmic contacts top‐type ZnTe were investigated using the transmission line model method and cross‐sectional transmission electron microscopy. The specific contact resistance decreases when the annealing temperature is increased and reaches a minimum at 300 °C. The formation of NiTe2from the reaction between Ni and ZnTe plays an important role in lowering the contact resistance. A contact stability test performed at 102 °C suggests that these ohmic contacts are stable even under high‐current injection. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115500

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

AlGaNpnhomo‐ and heterojunctions were fabricated on silicon carbide substrates by metalorganic chemical vapor deposition. AlN concentration in AlGaN layers ranged from 2 to 8 mol %. Mesa structures were made by reactive ion etching. Electroluminescence (EL) from AlGaNpnjunctions was studied. EL peaks associated with near band‐to‐band transition in AlGaN were detected. The minimum wavelength of EL peak of ∼348 nm (h&ngr;∼3.56 eV, 300 K) was measured for ap‐Al0.08GaN0.92/n‐Al0.06Ga0.94N heterojunction. The dependence of the photon energy of the edge EL peak on AlN concentration in AlGaN was measured. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115501

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a sensitive optical technique that allows two‐dimensional mapping of subsurface inhomogeneities of semiconductors. Using this contactless, room temperature technique, which is based on differential reflectance spectroscopy, we have been able to generate relief maps which show the spatial distribution of damage/defects in a number of III–V compounds and Si. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115502

出版商:AIP    

年代:1995

数据来源: AIP