InAs/GaAs和InAs/InxGa1-xAs/GaAs纳米线异质结构的生长研究

利用金辅助金属有机化学气相沉淀法(MOCVD)在GaAs(111)B衬底上分别制备了InAs/GaAs和InAs/In _{x Ga1-xAs/GaAs(0≤x≤1)纳米线异质结构.实验结果显示,直接生长在GaAs纳米线上的InAs纳米线生长方向杂乱或者沿着GaAs纳米线侧壁向衬底方向生长,生长的含有In x Ga1-xAs组分渐变缓冲段的InAs/In x Ga1-x关键词： 纳米线异质结构 xGa1-xAs')" href="#">InxGa1-xAs 组分渐变缓冲层 金属有机化学气相沉淀法}     

Sulfur diffusion into GaAs/Ga0.7Al0.3As heterostructures for device applications

0.7 Al_0.3As heterostructure layers grown by liquid phase epitaxy. GaS and As in a weight ratio of 2:1 were used as the diffusion sources. The source of GaS was carefully selected via X-ray diffraction analysis. Sulfur diffusion was carried out in a sealed quartz ampoule at a temperature of 820 °C and an arsenic pressure of 1 atmosphere. The carrier concentration profile from experimental results agrees well with the theoretical profile, which was calculated with the complementary error function solution assuming a segregation coefficient of m=1 at the hetero-junction interface. A smooth diffusion of sulfur was observed without any surface damage or hetero-interface defects. A double heterostructure laser was fabricated by employing sulfur diffusion. Cathode luminescence intensity analysis revealed that no damage was caused by sulfur diffusion at the active layer. Excellent characteristics such as a long life, a low threshold current, a fundamental transverse mode oscillation and a high modulation speed were obtained. Received: 1 June 1998/Accepted: 10 August 1998     

Negative and persistent photoconductivity in p-type Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As heterostructures under uniaxial stress

Abstract

Illumination of a double p-Al_0.5Ga_0.5As/GaAs/Al_0.5Ga_0.5As heterostructure by a red light emitting diode results in a negative photoconductivity that, after the diode is switched off, slowly relaxes to a positive persistent photoconductivity, characterised by an approximately 1.5-fold increase of the two-dimensional hole concentration. This metastable state may be explained with a model in which deep electron traps are supposed to be located above the Fermi level on the inverted heterointerface. Under uni-axial compression the hole concentration in the persistent photoconductivity state, as well as in the dark state, demonstrates the same linear decrease.     

Study of two-dimensional hole gas concentration and hole mobility in zinc delta-doped GaAs and pseudomorphic GaAs/In0.2Ga0.8As heterostructures

Zinc delta-doped GaAs and pseudomorphic GaAs/In}_0.2Ga_0.8As heterostructures grown by low-pressure metalorganic chemical vapour deposition have been demonstrated. The influence of delta-doping period and spacer thickness on two-dimensional hole gas concentrations and hole mobility was studied. From secondary-ion mass spectroscopy and Hall measurement, we conclude that zinc delta-doping can form an excellent abrupt profile (full-width at half maximum is of 10 nm) and offer a high two-dimensional hole gas sheet density (as high as 1 × 10¹³cm⁻²) By adopting a strained InGaAs material as the active channel and by carefully modulating the spacer layer thickness, one can obtain a significantly enhanced hole mobility.     

Anomalous behavior of excitons at light holes in strained (In, Ga)As/GaAs heterostructures

Additional localization of holes due to Coulomb attraction to the electron located in a quantum well is important for light-hole excitons in the heterostructure (In, Ga)As/GaAs. The fine structure of the optical and magneto-optical spectra of these quantum wells is examined in detail with the formation of a “Coulomb well” and deformations taken into account. Fiz. Tverd. Tela (St. Petersburg) 40, 797–799 (May 1998)     

Properties of MnSb/GaAs heterostructures

MnSb layers are deposited on GaAs(100) via the laser ablation of Mn and Sb targets. The magnetic field dependences of the transverse Kerr effect display magnetic anisotropy and magnetization jumps. Measurements of the Hall effect reveal a hysteresis loop at temperatures of up to 300 K.     

Smith Purcell effect in GaAs/AlGaAs heterostructures

We report a new experimental technique to study the form of the hot electron distribution function in GaAs/AlGaAs heterostructures. A weak periodic surface potential induces Smith-Purcell-FIR-radiation of the electric field driven hot electrons in the 2-dimensional electron gas directly reflecting their velocity distribution. The FIR- radiation is detected by a magnetic field tuned InSb-detector. In samples with very low electron concentration and high mobility the emission spectra show a significant shift to higher energies and develop a steep high energy slope with increasing electric field when we use the geometry with grating vector q directed parallel to the electric field (q ∥ E). In the geometry q ⊥ E smooth decays are observed at lower energies. Comparison of the results with theory gives experimental evidence of a non-equilibrium shape of the distribution caused by the onset of LO-Phonon emission. In addition, the hot electron mean free path of the heated distribution is derived by investigating the experimental emission spectra as a function of the grating period length. The influence of a limited hot electron mean free path on the spectral width is described in terms of a Fourier-analysis of the interaction potential. In drift direction a mean free path of λ = 200 nm is obtained, whereas the mean free path is smaller in the direction perpendicular to the drift direction.     

Scaled nano-and microrelief of ordering regions in Al x Ga1 − x As/GaAs(100) epitaxial heterostructures

The Al _x Ga_{1 ? x} As/GaAs(100) heterostructures grown by MOS hydride epitaxy were studied using atomic force and scanning electron microscopy. Regions with an ordered nanorelief with a period of approximately 115 nm were discovered on the surface of the sample with x ～ 0.50. An AlGaAs₂ superstructural phase appears in these regions.     

Origin of current instability in GaAs/AlGaAs heterostructures

We propose a mechanism to explain the electric instability often observed in modulation-doped heterostructures GaAs/AlGaAs when current is passed along the heterostructure layers. The instability is caused by hot electron transport in AlGaAs layer that is not only heavily doped, but also strongly compensated due to the presence of DX-centers. This layer contains a large-scale random potential of significant magnitude, which strongly affects electron transport. The heating of electrons in the percolation cluster net and electron transfer from the cluster into the random potential wells result in the appearance of latent negative differential conductivity causing the current instability. When the instability gives rise to the formation of a high electric field domain, one of the domain walls blocks the current flow through the two-dimensional electron gas. Experimental results supporting this mechanism are given.     

X-ray double-crystal rocking curves in GaAlAs/GaAs heterostructures

Summary X-ray double-crystal rocking curves of Ga_1−x Al _x As/GaAs heterostructures have been calculated using a dynamical diffraction model for the general case of Bragg reflection geometry. Different experimental configurations have been considered and the possibility of studying both slightly mismatched and relatively thin layers has been investigated. Experimental rocking curves have been measured using the CuKα ₁ radiation, the 004 symmetric reflection and a perfect crystal as the monochromator. An excellent agreement between calculated and experimental rocking curves has been found and this demonstrates the reliability of both the experimental procedure and the theoretical approach.     

Composition fluctuations in dilute nitride (Ga,In)(N,As)/GaAs heterostructures measured by low-loss electron energy-loss spectroscopy

We report on the investigation of composition fluctuations in epitaxially grown (Ga,In)(N,As) epilayers on GaAs(001) substrates by using electron energy-loss spectroscopy (EELS). The N and In concentrations are determined locally with a probe size of about 8 nm from the low-loss EELS measurements. We demonstrate that the small amount of N incorporating in dilute nitride alloys can be measured quantitatively by the plasmon energy shift with respect to a GaAs reference, and that the In content is analyzed simultaneously from the In 4d transitions, which have been isolated from the overlapping Ga 3d transitions. Our spatially resolved EELS results are utilized to discuss the origin of the inherent composition fluctuations and their influences on the morphological instabilities during epitaxial growth.     

Ordering effects in InGaP/GaAs and InGaAsP/GaAs heterostructures grown by LP-MOVPE

Summary The cationic ordering in InGaP epilayers grown by low-pressure vapour phase epitaxy on GaAs substrates has been investigated by X-ray diffraction. The effects of both the substrate miscut and the doping with Si and Zn have been studied. It has been found that ordering effects occur inside relatively small domains on (1–11) and (−111) planes; however, by increasing the miscut angle the domains of the first kind tend to increase their dimensions, while the second ones tend to disappear. Moreover, doping with impurities substituting cations is seen to destroy the order. Photoluminescence anomalies have been revealed and correlated to the size and ordering degree of the ordered domain.