砷化镓材料与激光相互作用的实验研究

从实验的角度对本征砷化镓与激光的相互作用进行了研究。首先,采用不同功率的Ｎｄ：ＹＡＧ连续激光对该材料进行照射,观察其电导的变化。实验中发现,砷化镓材料对大于其长波限１．０６μｍ的激光有明显的吸收,并表现出光电导现象。对实验现象进行了分析,并对其相应的吸收机理进行了讨论。其次,对于受激光作用后的砷化镓材料样品,利用扫描电镜进行分析,得以观察到激光对材料的热学损伤效果。     

Fundamentals and applications of photonic waveguides with bound states in the continuum

Photonic waveguides are the most fundamental element for photonic integrated circuits(PICs). Waveguide properties, such as propagation loss, modal areas, nonlinear coefficients, etc., directly determine the functionalities and performance of PICs. Recently, the emerging waveguides with bound states in the continuum(BICs) have opened new opportunities for PICs because of their special properties in resonance and radiation. Here, we review the recent progress of PICs composed of waveguides with BI...     

Effect of the diameter of the photoexcited region on the picosecond relaxation of bleaching in a thin layer of GaAs

It is found experimentally that the relaxation of bleaching in GaAs, which takes place when charge carriers are photogenerated by a high-power picosecond optical pulse, is slowed as the beam diameter F increases. Relaxation of the bleaching is caused by a decrease in the concentration of carriers due to recombination-induced superluminescence in GaAs. It is found that as the diameter F increases, the rate of superluminescence recombination slows, although the intensity of the superluminescent emission should increase. This apparent contradiction is explained with the help of theory. Fiz. Tekh. Poluprovodn. 32, 542–545 (May 1998)     

Recombination in the space charge region and its effect on the transmittance of bipolar transistors

AbstractThe effect of recombination in the space charge region of the emitter junction on the transmittance of bipolar transistors is considered. Measurements of the transmittance of several commercial transistors at low injection levels essentially agree with theoretical values given by the expressions obtained here, which take into account deep levels and recombination through them. Fiz. Tekh. Poluprovodn. 31, 1146–1150 (September 1997)     

On the characterization of surface states and deep traps in GaAs MESFETs

A simple model of frequency-dependent transconductance (g′_m(f)) is developed for characterizing surface states and bulk traps in GaAs metal semiconductor field effect transistors (MESFETs) by considering the occupancy modulation of the surface states and bulk traps. It is shown that the transconductance dispersion provides information for the determination of surface state and bulk trap energy levels. In particular, it is shown that the peak frequency in the transconductance spectrum, dg′_m(f)/df vs f, is equal to the characteristic frequency of a surface state or a bulk trap that is responsible for the peak. Thus, the temperature dependence of the peak frequency facilitates the measurement of the surface state or bulk trap energy level. It is found that peaks due to surface states can be distinguished from those due to bulk traps in the gated channel region by their different dependence of peak heights on the gate-source reverse bias. A comparison of the theoretical results and the available experimental observations shows that the model can successfully explain both the surface leakage current dependence of transconductance dispersion magnitude reported by Ozeki et al. [Inst. Phys. Conf. Ser., No. 63, pp. 323–328 (1982)] and the temperature dependence of transconductance dispersion observed by Blight et al. [IEEE Trans. Electron Devices ED-35, 257–267 (1988)].     

Spatial-time dynamics of the discharge pumping and lasing in a XeClexcimer laser

Spatial-time density distributions of excited components (Xe*, He*, Xe⁺*, XeCl*, free electrons) and the lasing intensity were measured by the pulse-dye-laser absorption (gain) probing of the active medium of a XeCl discharge laser. Some general regularities of the local deposition rate dynamics and active medium formation processes have been obtained. The influence of the electric field and preionization nonuniformities on the discharge profile is discussed. It is shown that the spatial profile, for the number of plasmochemical reactions leading to the formation of this component. The effect of the discharge layering is explained on the basis of the density gradients of excited on the basis of the density gradients if excited components and the oscillating pumping     

Intersubband absorption of TE and TM waves in p-type semiconductorsuperlattice including the effects of continuum states

We present theoretical results for the absorption coefficients for both TE and TM waves due to intersubband transitions within the valence subbands of a p-type superlattice. Both the bound and continuum states are included in our calculation. The continuum states are discretized by applying a periodic boundary condition. Numerical results are illustrated for different well and barrier widths. The results show that the intersubband transitions among the bound states result in sharp resonance absorption while the intersubband transitions between bound states and continuum states give a broad maximum at a photon energy larger than the barrier height. The TE and TM absorption coefficients are comparable in magnitude. Our theoretical results are in agreement with recent experimental observations on bound states to continuum states transitions     

Ultrafast self-modulation of the optical absorption spectrum under conditions of both the ultrashort optical pumping and superluminescence in GaAs

Self-modulation of the optical absorption spectrum is observed during the picosecond photogeneration of charge carriers and intense superluminescence in GaAs. As the picosecond delay τ of the probing pulse with respect to the pump pulse is varied in the region of τ < 0, the local points of the absorption intensification (juts) shift along the spectrum (the modulation resembles a running wave). As the value of τ is varied in the vicinity of τ = 0, the juts in the spectrum arise and disappear at approximately fixed photon energies (the modulation resembles a standing wave). At certain photon energies, the dependence of the rate of variation in the absorption coefficient dα/dτ on τ is found to be modulated by pulsations, similarly to the previously observed modulation of the picosecond stimulated emission from GaAs. Presumably, the spectrum self-modulation represents (and, thus, reveals) the modulation of the electron distribution in the conduction band. This modulation is caused by the fact that the evolution of the electron-population depletion at the bottom of the conduction band during superluminescence reflects (due to the electron-phonon interaction) on the population of the upper energy levels in the band.     

Terahertz emission and photoconductivity in n-type GaAs/AlGaAs quantum wells: the role of resonant impurity states

Terahertz emission spectra in a longitudinal electric field and lateral photoconductivity spectra under terahertz illumination have been studied in structures with GaAs/AlGaAs quantum wells (QWs). It is shown that the spectra contain features associated with electron transitions involving resonant impurity states related to the second quantum-well subband. Calculations of the energy spectrum of impurity states and matrix elements of optical transitions made by taking into account various positions of the impurity relative to the QW center confirm the assumptions made.     

Characterization of deep centers in undoped semi-insulating GaAs substrates by normalized thermally stimulated current spectroscopy: Comparison of 100 and 150 mm wafers

A well-established characterization method for investigating deep traps in semi-insulating (SI) GaAs is thermally stimulated current (TSC) spectroscopy; however, TSC is not considered to be a quantitative technique because it involves carrier mobility, lifetime, and geometric factors, which are either unknown or poorly known. In this paper, we first show how to quantify a TSC spectrum, by normalizing with infrared (hv = 1.13 eV) photocurrent, and then apply this method (called NTSC) to study the lateral uniformity of the main deep centers across the diameters of undoped SI GaAs wafers. The wafers used in the study include both the standard 100 mm sizes and the new 150 mm variations, and are grown by both the low and high pressure liquid encapsulated Czochralski techniques. The results reveal that the 150 mm wafers have a worse NTSC uniformity for the main traps and a higher degree of compensation, as compared these parameters for the 100 mm wafers. In addition, nonuniformities related to the electric field effects on both the TSC spectrum and the low temperature photocurrent are found in the 150 mm wafer grown by the low pressure technique.     

Subterahertz self-oscillations of depletion of electron populations in the conduction band of GaAs in the presence of pumping and intrinsic stimulated radiation

It was previously found that, during picosecond optical pumping, ultrafast interrelated self-modulations of fundamental absorption of light and intrinsic stimulated picosecond radiation emerge in GaAs. In this study, quantitative evaluations confirming the assumption that the mentioned self-modulations are caused by self-oscillations of depletion of electron populations in the conduction band are made. The relation for the frequency of self-oscillations of depletion of populations is obtained. The presence of conditions for self-organization leading to the emergence of periodic nonlinear waves in nonequilibrium media, which is photogenerated electron-hole plasma with depletions of populations, is shown. As a result, in a series of studies, including this one, it is found that the collective excitation of charge carriers—self-oscillations of depletion of populations of the conduction band—emerges during pumping in GaAs under the effect of intrinsic stimulated radiation.     

激光等离子体相互作用中量子电动力学效应对激光能量吸收的影响

为了研究强激光与等离子体相互作用中的量子电动力学(QED)效应对激光能量吸收的影响,用理论方法对强度为I>10^22wcm^-2、反方向传播的两束圆极化强激光与等离子体固体靶相互作用过程进行研究。探讨经典和QED情况下的辐射阻尼效应对激光能量吸收的影响。结果表明,在QED情况下,在相互作用过程中能够产生高能电子和高能辐射。这些高能电子集体振荡过程中的辐射阻尼导致激光能量的强吸收。QED情况比经典情况具有更好的实际应用价值。     

Band-tailing effects and the temperature dependence of radiative recombination in compensated epitaxial GaAs laser junctions

The temperature dependence of the spectrum, threshold current, and power output of compensated vapor-grown epitaxial GaAs lasers and incoherent emitters near room temperature is presented. It was found that an increase in temperature produced a narrowing of the spontaneous emission spectrum. This narrowing has been attributed to a movement of the Fermi level through an exponential density-of-states tail.     

Optical pumping of CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers by means of a new pulsed CO/sub 2/ laser: characterization of new far-infrared laser emissions

We have reinvestigated CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers as sources of far-infrared laser radiation using the optical pumping technique. A new waveguide pulsed CO/sub 2/ laser was used, that delivers high peak powers also in the 10-HP CO/sub 2/ band and has allowed us to observe 19 new far-infrared emissions from CHD/sub 2/OH and 8 new far-infrared emissions from CH/sub 2/DOH. Each of them is characterized in wavelength, pump offset from the center of the exciting CO/sub 2/ line, relative polarization, optimum operating pressure and intensity.     

Electron states in the surface region of gallium arsenide treated in selenium and arsenic vapor

The parameters of charge localization centers in the skin layer of gallium arsenide treated in selenium-arsenic vapor are investigated by deep-layer transient spectroscopy. It is established that the addition of arsenic to the vapor phase slows down the reaction of heterovalent substitution of selenium for arsenic in GaAs and reduces the density of centers in the skin layer of GaAs. Fiz. Tekh. Poluprovodn. 33, 719–722 (June 1999)     

The Stark shift of the hole states in separate InAs/GaAs quantum dots grown on (100) and (311)A GaAs substrates

Deep-level transient spectroscopy is used to study charge-carrier emission from the states of separate quantum dots in InAs/GaAs p-n heterostructures grown on (100)-and (311)A-oriented GaAs substrates in relation to the reverse-bias voltage U. It is established that the structures under consideration exhibit different bias-voltage dependences of the Stark shift for the energy levels of the quantum-dot states on the value of U.     

Optical investigation of the relaxation process in InGaAs/GaAs single strained quantum wells grown on (001) and (111)B GaAs substrates

Molecular Beam Epitaxy (MBE) growth of a series of Single Strained Quantum Wells (SSQWs) of InGaAs/GaAs with indium content ranging from 10% to 35% and 100 Å well thickness was performed on (001) and (111)B GaAs substrates under optimized growth conditions for simultaneous growth. The Critical Layer Thickness (CLT) of the heterostructures grown on both substrates was comparatively studied by low temperature Photoluminescence (PL). Relaxation is readily observed in the structures grown on (001) GaAs for 24% In-content. This value is in close agreement with both a calculation of the excess strain associated with the two Matthews and Blakeslee strain relieving dislocation mechanisms and the onset of three-dimensional growth. By contrast, heterostructures grown on (111)B GaAs remain pseudomorphic for In-contents above 25%. A maximum PL peak wavelength of 1.1 microns at room temperature has been reached under the growth conditions used. This would correspond to an In-content around 31%. The study shows that (111)B is a preferable choice of substrate orientation for the growth of InGaAs/GaAs heterostructures for optoelectronic applications at wavelengths beyond 1 μm.