摘要:

ZnS0.1Se0.9/ZnSe strained layer superlattices with up to 120 periods were grown by metalorganic vapor phase epitaxy. We demonstrate the sensitivity of room temperature photoluminescence of these structures for the assessment of the dependence of structural properties on growth conditions. Low temperature photoluminescence (PL) and x‐ray diffraction data confirm the results of the room temperature PL measurements. In optimized samples showing highly efficient blue luminescence (2.71 eV) at 300 K heavy‐hole and light‐hole free exciton recombinations at 11 K and higher‐order satellite reflections in the x‐ray diffraction profiles were observed.

ISSN:0021-8979    

DOI:10.1063/1.354162

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Ge‐Ag ohmic contacts with good dimensional control to a two dimensional electron gas operating at low temperatures are demonstrated. At 4.2 K, the specific contact resistance lies in the range 2–5 &OHgr; mm for anneals between 520 and 560 °C. The surface morphology is smooth, and the edge definition is of the order of 100 nm. Secondary ion mass spectroscopy analysis indicates that Ge diffusion is limited to within 2000 A˚ of the surface for a concentration of 1017cm−3in samples annealed at 540 °C and below.

ISSN:0021-8979    

DOI:10.1063/1.354163

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have studied the giant magnetoresistance of two sputtered systems, Co/Cu multilayerswithandwithoutFe buffer layers, with respect to their magnetic and structural properties. A different oscillatory character of the magnetoresistance as a function of Cu interlayer thickness was found for these two series. The specimens were magnetically characterized using a vibrating sample magnetometer. Transmission electron microscope cross‐sectional images and low‐angle x‐ray diffraction analysis indicated a very different quality of the multilayer structure for these two systems. This is assumed to be the reason for their different magnetoresistant behavior.

ISSN:0021-8979    

DOI:10.1063/1.354164

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We used spectroscopic ellipsometry to analyze the refractive index and the absorption coefficient of thin buffer layers of InP grown by metalorganic vapor phase epitaxy on Si substrates. We found a pronounced influence on the crystallographic properties of the subsequently grown InP main layer. The drastically increased optical absorption of the buffer layers is possibly caused by a high density in misfit dislocations or twins originating from the difference in lattice constants of InP and Si.

ISSN:0021-8979    

DOI:10.1063/1.354165

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We propose a novel electronic quantum interferometer which exhibits strong quantum interference effects in the ballistic regime. This behavior is produced without introducing additional barriers along the electronic path. Rather, by modulating the channel width of one of the arms in a multiply connected quantum nanoconstriction, one can produce an effect similar to that of an applied retarding gate potential. Strong conductance oscillations are then produced by quantum interference between phase‐lagged propagating subbands in the different channels. We present results for typical structures, and discuss the dependence of these effects on electron path length and temperature.

ISSN:0021-8979    

DOI:10.1063/1.354166

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Spectral transmission, reflection, and photocurrent absorption data obtained on gas‐source molecular beam epitaxy grown InGaAs/InP multiple quantum well (MQW) and superlatticep‐i‐ndiode structures demonstrate, for the first time in this materials system, that similar modulation to MQW structures can be achieved using superlattices, but at significantly lower operating voltages. Specifically, we have observed photocurrent absorption changes of as much as 58%, transmission changes of 8.2%, and reflection changes of 32% for applied biases of only 4 V, in nonresonant modulators operating at a wavelength ∼1.5 &mgr;m. These results encourage the possibility of employing such devices in fast, high density optical modulator arrays operating over the 1.3–1.6 &mgr;m range.

ISSN:0021-8979    

DOI:10.1063/1.355305

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The model of Alessandro, Beatrice, Bertotti, and Montorsi [J. Appl. Phys.68, 2901 (1990)] is used to derive the Barkhausen noise power integrated over all frequencies. Using the magnetomechanical hysteresis model of Sablik and Jiles [IEEE Trans. Magn.29, 2113 (1993)], it is then shown how the Barkhausen noise power peaks at a magnetic fieldHlarger than theHvalue at which the magnetic permeability peaks. Variation with respect to applied stress and with respect to field ramp rateH˙ is also investigated. The almost linear increase of Barkhausen amplitude with applied stress seen experimentally is confirmed by the model.

ISSN:0021-8979    

DOI:10.1063/1.354167

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Single crystal GaN thin films resulting from various deposition techniques are usually dominated by residual donors. To date, the true nature of this donor conduction is not known. Nitrogen vacancies, residual oxygen, and growth defects are cited as potential causes for the residualn‐type conduction. In this communication we present the first systematic study of near conduction band edge states inn‐type GaN samples deposited over basal plane sapphire substrates using low pressure metal organic chemical vapor deposition. Electron spin resonance, low temperature photoluminescence, and Van der Pauw–Hall measurements were used as the basis for our study. We concluded that the residualn‐type conduction in GaN results from a band of delocalized donors.

ISSN:0021-8979    

DOI:10.1063/1.354168

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We report the fabrication and properties ofp‐InP:n‐amorphous silicon heterojunctions. The good rectification ratio of 1000:1 at 0.5 V, and existence of straight‐line capacitance curves, indicated a sharp interface of good quality. Optical internal photoemission measurements under various bias conditions showed that the band offsets were 0.06 and 0.37 eV for the valence and conduction bands, respectively. Photovoltaic action resulted in open circuit voltages of over 0.9 V at air mass 2 solar illumination and efficiencies of over 9%.

ISSN:0021-8979    

DOI:10.1063/1.354169

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

We have studied III‐V semiconductor dot samples with Raman microscopy. The samples were fabricated by electron beam lithography and dry etching. The non‐resonant Raman scattering can provide direct information on the structure alteration and associated phonon bands. Direct Raman band imaging reveals the uniformity of the GaAs micrometer‐sized dot arrays.

ISSN:0021-8979    

DOI:10.1063/1.354170

出版商:AIP    

年代:1993

数据来源: AIP