最新刊期
卷 7 ， 期 3 ， 1986
- 摘要：Doping superlattices (nipi structures) have been grown in InP using organometallic vapor phase epitaxy in an atmospheric pressure reactor using trimethylindium and phosphine. The unintential doping levels in InP employed in these experiments were as low as 8×1013cm-3 and 300K mobilities as high as 5744cm2/V·s. The n- and p- type dopants were diethyltel-lurium and dimethylzinc, respectivly, both n-, p- carrier concentritions can be up to 1019cm-3. Such structures have been characterized using low temperature photoluminescence at various excitation intensities,time decay, time resolved photoluminescence, and photo-reflectance experiments. The 4K photoluminescence spectra at various excitation intensities are presented for a structure consisting of six 200Å layers with doping levels of 1×1018 and 2×1018cm-3 for the n- and p-layers. The luminescence peak is found to occur at energies considerable less the band gap of InP and to move to higher energies with increased excitation intensity, as expected for doping superlattices where the band gap,which is indirect in real space, increases with increasing excited carrier concentration. The total photoluminescence signal decays in several steps, each exponential,with time constants ranging from 6×10-8 to 7×10-4 seconds at 4K.Typical of these spatially indirect band gap materials. Quantum size effects existing in InP doping superlattices have also been probed with photo-reflectance technique. All experimental results are in good agreements with model calculations, which assume a parabolic well to describe the quantum size effects in InP doping superlattices.140|97|0更新时间：2020-08-11
- 摘要：Ⅲ-Ⅴ compound GaN has the Wurtzite crystal structure[1] and belongs to symmetry group Vβγ For GaN, group theory predicts the following lattice phonons: A1 branch in which the Raman-active phonon is polarized in the z direction and which is infrared active also, and E1 branch in which the phonon polarized in the x, y plane can be observed in both infrared and Raman experiments, two E2 branches which are Raman active and two silent B1 modes[2,3]. The A1 and E1 modes can be split into longitudinal (LO) and transverse (TO) components by the macroscopic electric field associated with the longitudinal phonon.Volia Lemos et al. [E]have observed three Raman active optical phonon modes E2, A1(TO) and E1 (TO) in GaN epitaxy layer grown by vapor phase epitaxy (VPE) on sapphire substrate, No E1 (LO)mode was. observed in Raman scattering experiment previously[4,5].The present work shows a Raman scattering experimental result in un-doped N-GaN samples grown on (0001) oriented sapphire substrate by VPE. An Ar+ laser was used as the excitation source.117|92|0更新时间：2020-08-11
- 摘要：Light induced electron spin polarization is an important consequence of charge separation in the primary photoreactions of photosynthesis.The informations on the structure and constituent of the primary photoreactions and their interaction could be obtained. In this paper, P-700+and A1-centers were studied in PSI of the intact soybean leaves with ESR techniques and curve fits at room temperature. For ESR measurements, the leaves were irradiated with ultraviolet light(337.1nm) and cw He-Ne laser. When orientation of the intact soybean leaves was changed in the magnetic field, we observed the dependence of electron spin polarization on the orientation.Our choice of the leaves for this study was based on the current model of the PSI reaction center organization, which may be represented as P-700A1XFdBFdA. According to the radical pair theory, we could write an approximate spin Hamiltonian of P-700+and A1-radical pair asH=βH0·((gD·SD+gD·SA)-J(2SD·SA+1/2)+ΣAi(D)Ii(D)·SD+ΣAi(A)Ii(A)SAand the experimental ESR intensity Ip-700+of P-700+as a function of field position H is given by IP-700+(H)=Σ-(pi)e(H-Hi)2/δ2.96|69|0更新时间：2020-08-11
- 摘要：The absorption spectra of Ho3+:YLiF4 and Er3+:YLiF4 crystals were measured in detail. The formula we use to calculate the experimental oscil-lator strength is Pexp=4.318×10-9∫ε(σ)dρ(l)where,ε(σ) is the extinction coefficient of gram mole, σ the wavenumber.107|46|0更新时间：2020-08-11
- 摘要：This paper gave the simulation of the 5D0,1→7FJ line-to-line transition probabilities in Na5Eu(MO4)4(M=Mo,W)hosts according to the Judd-Ofelt theory.The Wave-functions of the 5D and 7F levels were derived from the crystal field calculation made in a basis of 671 |SLJM> levels including J-mixing. The wave-functions were used to calculate the m.d. and e.d. matrix elements.107|46|0更新时间：2020-08-11
- 摘要：The investigation of tunable solid-state laser crystal attracted many scientists in the past years. To search new compounds with garnet structure was one of the main fields. YGG:Cr is a laser crystal with prospects, but its spectral properties have not been investigated thoroughly yet.In YGG:Cr,Cr3+ substituted Ga ions located at slightly trigonal distorted octahedral site. Its 2E energy level affected by non-octahedral crystal field and spin-orbit couple was splited up into E and 2A. As shown in the absorption spectrum, the splitting was small, so we used the crystal field parameters of Ok group to fit the energy levels of Cr3+ . Referring the Tanabe-Sugano energy levels diagram of d3 electron, the peaks and bands in the absorption spectrum were assigned. The fitting results were in agreement with the experimental data very well. By data fitting, the crystal field parameters Dq, B and C were obtained. Based on Huang Kun theory, Huang Kun factor S and average phonon energy hω, were derived from the experimental data.114|81|0更新时间：2020-08-11
- 摘要：Ga1-xAlxAs red DH LED shown in Fig.1 has been prepared.Compared with SH device its luminous flux has remarkably increased and reached 22mLm at 20mA.There is a stronger infrared peak at about 890 nm in EL spectrum besides a red main peak. It is found that the relative intensity of the infrared band to the red one is related to the luminous efficiency of devices.The stronger the infrared emission is, the poorer the efficiency(see Table 1). This implies that a part of injection energy is expended in generating the infrared emission which does not contribute to luminous flux. Therefore, to find out the origin of the infrared emission and then to eliminate it will raise the luminous efficiency of devices in the furture.108|58|0更新时间：2020-08-11
- 摘要：The abrupt degradation characteristics of the InGaAsP/InP DH LEDs were studied. The InGaAsP/InP DH wafers were grown by LPE technique. It consisted of three or four layers. The First n-InP layer was a 5-8μm thick buffer layer doped with Sn or Te. The second one was an undoped active layer approximately 1-2μm thick. The third was confining layer of p-InP (2-3μm thick) doped with Zn. The last was Zn doped contact layer. The concentration in the active layer was measured electrochemically with C-V methode. The devices are smallarea, surface emitting diodes.The degradation characteristics of the InGaAsP/InP DH LEDs were investigated at room temperature, 70 and 85℃ and with and without injetc current respectively. The experiment was carried out in air and one hundred devices fabricated from different wafers were used.When aging dark defects in the LEDs are observed with an infrared line scanner.The effects of the inject current, environment temperature,active layer concentration and solder on the degradation characteristics of the devices were investigated. The results showed that the forward anomalous I-V characteristics (i.e.Vf/Vf0≈0,V/V0<1) were directly responsible for the abrupt degradation.The EL pattern is homogeneous even the LEDs operate for 1000hrs at a current of 100mA at 85℃.The DSD's are sometimes generated in the emitting area when aging at 70 and 85℃ for over lOOOhrs, but they are not the reason for the abrupt degradation.99|71|0更新时间：2020-08-11
- 摘要：A low temperature photoluminescence (PL) measurement facility connected with an IBM-PC microcomputer is set up for PL measurement of solid state materials especially for Ⅲ-Ⅴ and ,Ⅱ-Ⅴ semiconductor compounds. It is named as PL-PC and as shown in Fig.1. The system is interfaced with a data acquisition system (DAS) , the series 500 of Keithley Company of the United States. Convenient control and efficient data processes are demonstrated in PL-PC experiments.There are many special functions in this PL-PC system for automatic control and convenient use . (1) The spectrum monochromator and chart recorder can be started and stopped automatically by the control of computer key board, or by the designed program. The intensity of input signal can be checked and the output signal would be automatically adjusted by the program. (2) There are different data acquisition abilities, and they can be adjusted to fit varied situations. The resolution of measured spectrum can be chosen as fine as 0.04Å which is good enough for most of grating monochromators in which the resolution is only about 0.1Å. In the case of signal automeasurement,the lowest measurable value can be adjusted to find the fine structure in the PL spectrum. (3) Many data processes are set up by the Series 500. The wavelength and photon energy can be shown and calculated immediately. The intensity of spectrum is corrected according to the spectra responsibility of different detectors, such as the photomultiplier, Ge detector and so on, and can be smoothed to draw out a satisfactory curve. The position of the main peak of luminescence spectra and its full width at the half maximum value are given automatically.(4) The output data can be shown in a variety of ways:data curves on the computer display screen, the printer output and chart recorder curves. Also all of the data can be saved on the floppy disk, which may be used to compare with relevant PL results.In the computer system, soft 500 with basic language is successively used to control and plan all the PL measurement processes, A menu block structure is set up, and all the control orders can be shown on the screen to guide the operator to select and to use this system easily. A PL measurement result of semiconductor HgI2 with this PL-PC system is given to show the characteristics of output data. This system is helpful for PL experiment and can be expanded to other physical test applications, such as DLTS and optical waveguide measurement.This work was finished in Dept. of ECE, UCSB, U. S. A. Thanks are indebted to Prof. J.L.Merz and the optoelectronics research group for their helps.110|33|0更新时间：2020-08-11
- 摘要：The experimental system of laser-induced fluorescence (LIF)which uses the UV (λ=365nm) light of pulsed Xe1v ion laser with coaxial structure as the exciting source is described. The UV output characteristic of pulsed Xe1v ion laser was studied. It is the first time to use such a system to investigate the luminescence performance of ZnCdS:Ag fluorescent screen for medical X-ray. The LIF technique, which has very high sensitivity, can be easily used to measure the fluorescent spectrum and lifetime simultaneously. Experimental results are consistent with those obtained by using other methods (e.g. using UV lamp or X-ray as exciting source). The LIF technique has the advantage of avoiding the damage of X-ray radiation to human body.103|38|0更新时间：2020-08-11
- 摘要：The principle feature, and application of the large screen display with an electron beam acid-allergic colour-change film were described and the systematic analysjs of the optics and electron optics was made in detail.100|59|0更新时间：2020-08-11
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