Manganese-related luminescence in GaInAs/AlInAs multiple quantum wells grown on InP by molecular beam epitaxy

Two Mn-related luminescence peaks have been observed in a series of nominally undoped Ga_0.47In_0.53As/Al_0.48In_0.52As multiple quantum wells (MQW) grown lattice-matched on InP substrates by molecular beam epitaxy. These two peaks correspond to on-center and on-edge impurity states, respectively. The origin of the Mn impurities is outdiffusion from the Fe-doped semiinsulating InP substrate into the epitaxial layer. The binding energy of Mn acceptors, determined to be 53±3 meV in bulk-like Ga_0.47In_0.53As, increases to 80±5 meV for the on-center Mn state in a 58 Å MQW. The strong well-width dependence of the binding energy is explained in terms of the unique behavior of the Mn impurity in III–V semiconductors. The Mn in Ga_0.47In_0.53As and Ga_0.47In_0.53As/Al_0.48In_0.52As MQWs behaves predominantly as a deep impurity.On leave from: A. F. Ioffe Physicotechnical Institute, Leningrad, USSR     

Charge transport diagnosis by: I-V (resistivity), screening and Debye length, mean free path, Mott effect and Bohr radius in InAs, In0.53Ga0.47As and GaAs MBE epitaxial layers

We propose using collected galvano-magnetic data on MBE samples of n-type undoped epi-layers of InAs, In_0.57Ga_0.47As and GaAs on InP semi-insulating and GaAs semi-insulating substrates to characterize their charge transport properties. Hall concentration and resistance measurements vs. temperature were carried out, and these results allowed us to calculate the mean free path and magnetic length. However, they are mono-crystalline, they present multi-component charge transport structures. The characterization of these layers by means of a combined analysis of galvano-magnetic properties, I-V (resistivity), screening and Debye length, mean free path, Mott effect and Bohr radius characteristics gave new and very interesting results.The application of a previously described method of analysis also allows for the presence of a Mott transition to be determined. The presence of a Mott transition leads to the hypothesis that a part of conductance in such layers, especially at low temperatures may be due to an impurity band.We suppose either that during their epitaxial growth all of the investigated layers were unintentionally doped with excess atoms of one component, vacancies of other or that dangling bonds are present. Therefore, in the range of low temperatures, the possible and dominant conduction mechanism is conduction via such defects, with electrons moving by thermally activated hopping.     

Electromodulation spectroscopy of In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum wells

In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As quantum wells (QWs) of various widths have been grown by molecular beam epitaxy on the InP substrate and investigated by electromodulation spectroscopy, i.e. photoreflectance (PR) and contactless electroreflectance (CER). The optical transitions related to the QW barrier and the QW ground and excited states have been clearly observed in PR and CER spectra. The experimental QW transition energies have been compared with theoretical predictions based on an effective mass formalism model. A good agreement between experimental data and theoretical calculations has been observed when the conduction band offset for the In_0.53Ga_0.47As/In_0.53Ga_0.23Al_0.24As interface equals 60%. In addition, it has been concluded that the conduction band offset for the In_0.53Ga_0.23Al_0.24As/InP interface is close to zero. The obtained results show that InGa(Al)As alloys are very promising materials in the band gap engineering for structures grown on InP substrate.     

Particular nanowire superlattice as a spin filter

A nanowire superlattice of InAs and GaAs layers with In_0.47Ga_0.53As as the impure layers is proposed. The oft-neglected k³ Dresselhaus spin-orbit coupling causes the spin polarization of the electron but often can produce a limited spin polarization. In this nanowire superlattice, Dresselhaus term produce complete spin filtering by optimizing the distance between the In_0.47Ga_0.53As layers and the Indium (In) in the impure layers. The proposed structure is an optimized nanowire superlattice that can efficiently filter any component of electron spins according to its energy. In fact, this nanowire superlattice is an energy dependent spin filter structure.     

Ion-irradiated In0.53Ga0.47As photoconductive antennas for THz generation and detection at 1.55 μm wavelength

We present a detailed study of the photoconductive antennas made from heavy-ion-irradiated In_0.53Ga_0.47As material. The optical and transport properties of ion-irradiated In_0.53Ga_0.47As material are characterized. The terahertz waveforms emitted and detected by ion-irradiated In_0.53Ga_0.47As photoconductive antennas excited by 1.55 μm wavelength femtosecond laser pulses are reported and the effect of the carrier lifetime on the terahertz signal characteristics emitted by such devices is analysed. The performances of ion-irradiated In_0.53Ga_0.47As photoconductive antennas excited by 1.55 μm and also by 0.8 μm wavelength femtosecond laser pulses are compared to those of similar low-temperature-grown GaAs photoconductive antennas. To cite this article: J. Mangeney, P. Crozat, C. R. Physique 9 (2008).     

In0.53Ga0.47As/In0.52Al0.48As量子阱中双子带占据的二维电子气的输运特性

研究了不同沟道厚度的In_0.53Ga_0.47As/In_0.52Al_0.48As量子阱中双子带占据的二维电子气的输运特性.在考虑了两个子带电子之间的磁致子带间散射效应后,通过分析Shubnikov-de Haas振荡一阶微分的快速傅里叶变换结果,获得了每个子带电子的浓度、输运散射时间、量子散射时间以及子带之间的散射时间.结果表明,对于所研究的样品,第一子带电子受到的小角散射更强,这与第一子带电子受到了更强的电离杂质散射有 关键词： 二维电子气 散射时间 自洽计算     

Type-I and type-II Wannier-Stark effect in InGaAs/InGaAs superlattices

The formation of minibands is demonstrated in photocurrent experiments on shallow In_0.53Ga_0.47As/In_0.40Ga_0.60 As superlattices grown by low-pressure metal-organic vapor-phase epitaxy. Field-dependent variations of the spectral shape are attributed to Wanner-Stark localization. Both type-I transitions between electrons and heavy holes and type-II transitions involving light holes confined in the In_0.40Ga_0.60 As layers are observed and distinguished by their characteristic field dependence.     

Transport and magnetotransport properties of Mn-doped InxGa1−xAs/GaAs quantum well structures

We report on the transport, magnetotransport and magnetic properties of In_0.17Ga_0.83As quantum well in GaAs δ-doped by Mn. At low temperatures, the anomalous Hall effect was observed which detects the spin-polarized carriers. Negative magnetoresistance was found at low temperatures, which became positive at high temperature.     

赝形InxGa1-xAs/In0.52Al0.48As异质结构中二维电子气的回旋共振光谱研究

采用回旋共振光谱方法，同时获得了具有较高电子气浓度的赝形In_0.80Ga_0.20As/In_0.53Ga_0.47As/In_0.52Al_0.48AsHEMT结构中最低两个子能带的费密面附近电子有效质量、 散射时间和迁移率.观察到该系统中能带非抛物性和波函数穿透所导致的电子回旋有效质量的显著增大效应，以及合金无序势和电离杂质散射所引起的电子散射时间和迁移率明显的子带依赖性. 关键词：     

Dependence of current-voltage characteristics of pseudomorphic AlAs/In0.53a0.47s/InAs resonant tunneling diodes on quantum well widths

This paper studies the dependence of I-V characteristics on quantum well widths in AlAs/In_0.53Ga_0.47As and AlAs/In_0.53Ga_0.47As/InAs resonant tunneling structures grown on InP substrates. It shows that the peak and the valley current density in the negative differential resistance region are closely related with quantum well width. The measured peak current density, valley current densities and peak-to-valley current ratio of resonant tunneling diodes are continually decreasing with increasing well width.     

Electron g-factor in a gated InAs-inserted-channel In0.53Ga0.47As/In0.52Al0.48As heterostructure

We report on electron g-factor in an InAs-inserted In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructure. The gate voltage dependence of g-factor is obtained from the coincidence method. The obtained g-factor values are surprisingly smaller than the g-factor value of bulk InAs, and it is close to the bare g-factor value of In_0.53Ga_0.47As. The large change in g-factor is observed by applying the gate voltage. The obtained gate voltage dependence is not simply explained by the energy dependence of g-factor.     

Spatial variation of bandgap energy in In0.53Ga0.47As

We report the observation of spatial variation of the bandgap energy of In_0.53Ga_0.47As in high quality epitaxial samples grown lattice matched to InP. Nine samples grown by three different techniques (LPE, VPE and MBE) were investigated and they all showed this apparently random spatial variation. A bandgap variation as large as 15 meV was observed over distances of the order of 1 mm, an effect corresponding to two percent of bandgap energy.     

Comparison of tunneling times in isotropic and anisotropic media

We present a comparative analysis of the tunneling times of electromagnetic (EM) waves propagating in isotropic and anisotropic media. First, suitable expressions for the tunneling times in a layered periodic material, with anisotropic properties originating from its structure, are derived, followed by numerical calculations performed for a new type of anisotropic semiconductor metamaterial. In the first case, we have considered a layered structure which contains two differently doped In_0.53Ga_0.47As semiconductor layers. The second structure under investigation is made of alternately placed layers of doped In_0.53Ga_0.47As and undoped Al_0.48Ga_0.52As. The investigation of the dwell time as a function of incident wave frequency has revealed the existence of two peaks, one of which may be interpreted as a consequence of anisotropy, while the other one corresponds to the peak related to the absorption and the group delay. Both of these two peaks are affected by variations of layers?? doping densities. Furthermore, at increased incident angles of incoming EM waves, the dwell time peak occurs at the upper boundary of the frequency interval, for which the structure exhibits negative refractive index.     

Optical studies of In0.53Ga0.47As

We present luminescence data obtained as a function of temperature and excitation in In_0.53Ga_0.47As and In_0.7Ga_0.3As_0.63P_0.37. We assign the different lines and correlate the luminescence results with transmission measurements.     

Low-density band-filling in strained InAs quantum wells

We study the low-temperature photoluminescence (PL) of strained InAs single quantum wells (SQWs) embedded in a Ga_0.47In_0.53As matrix grown on InP substrates by modified solid-source molecular beam epitaxy. The spectra are interpreted in the frame of a two-level rate equation model describing the carrier dynamics in the structures. We show that band-filling occurs in these QWs for an excitation power as low as 30 Wcm^–2. Moreover, the spectra reveal that the band-filling results from the rapid population of the hole subband. This observation highlights the low in-plane heavy-hole mass in the compressively strained film. Our results therefore demonstrate the high potential of InAs/Ga_0.47In_0.53As QW nonlinear optical devices operating in the mid-IR wavelength range.     

Efficient spin filtering in a disordered semiconductor superlattice in the presence of Dresselhaus spin-orbit coupling

The influence of the Dresselhaus spin-orbit coupling on spin polarization by tunneling through a disordered semiconductor superlattice was investigated. The Dresselhaus spin-orbit coupling causes the spin polarization of the electron due to transmission possibilities difference between spin up and spin down electrons. The electron tunneling through a zinc-blende semiconductor superlattice with InAs and GaAs layers and two variable distance In_xGa_(1−x)As impurity layers was studied. One hundred percent spin polarization was obtained by optimizing the distance between two impurity layers and impurity percent in disordered layers in the presence of Dresselhaus spin-orbit coupling. In addition, the electron transmission probability through the mentioned superlattice is too much near to one and an efficient spin filtering was recommended.     

Analysis and evaluation of uniformity of SWIR InGaAs FPA—Part I: Material issues

The nonuniformity caused by fluctuations of indium composition, thickness and doping concentration of epitaxial absorption layer of InGaAs focal plane arrays (FPAs) is estimated theoretically with the incorporation of practical status. By the measurements on epitaxy wafers of 2 in. size, the fluctuation of indium composition is observed to be less than ±0.2% and ±1% for lattice matched In_0.53Ga_0.47As and wavelength extended In_0.80Ga_0.20As photodetector structures respectively, while the thickness and doping fluctuations are assumed to be the same. Results show that the response nonuniformity caused by fluctuation of indium composition is dependent on the target wavelength and can be neglected with a minor composition fluctuation if the cutoff wavelength is well set. The total response nonuniformity induced by the effects of thickness and doping fluctuations, which dominates the FPA performance for large signal applications, is estimated to be less than ±0.1% and ±0.5% for In_0.53Ga_0.47As and In_0.80Ga_0.20As FPAs smaller than 1 in. in maximum side length. Neglecting the effects of defects, the total detectivity nonuniformity caused by these fluctuations is about ±2% for In_0.53Ga_0.47As FPA and will reach up to about ±19% for In_0.80Ga_0.20As FPA, where the dark current nonuniformity due to the fluctuation of composition plays the most critical role.     

Luminescence in high purity In0.53Ga0.47As

We have investigated luminescence processes in high purity In_0.53Ga_0.47As grown by liquid phase epitaxy on InP substrate. The origins of luminescence processes have been determined by studying the dependence of emission intensity and spectrum on temperature. We show that exciton-ionized donor complex dominates the luminescence at 2K. With increasing temperature, the luminescence spectrum is dominated by donor-valence band and free electron-free hole recombination. Spectrum and bandgap energy are found to be dependent on the excitation position.     

Improvement of photoluminescence and electroluminescence characteristics of MBE-grown In0.53Ga0.47As/In0.53(Ga0.6Al0.4)0.47As quantum well laser structure with InGaAlAs digital alloys by thermal annealing

We investigated the effect of rapid thermal annealing (RTA) on the photoluminescence (PL) and electroluminescence of the In_0.53Ga_0.47As/In_0.53(Ga_0.6Al_0.4)_0.47As multiple quantum well (MQW) laser structure with InGaAlAs barrier layers provided by the digital-alloy technique. The SiO₂- (Si₃N₄-) capped samples followed by the RTA exhibited a significant improvement of PL intensity without any appreciable shifts in PL peak energy for settings of up to 750 °C (800 °C) for 45 s. This improvement is attributed to the annealing of nonradiative defects in InAlAs layers of digital-alloy InGaAlAs and partially those near the heterointerfaces of the digital-alloy layers. The InGaAs/InGaAlAs MQW laser diodes fabricated on the samples annealed at 850 °C show a hugely improved lasing performance. Received: 2 September 2002 / Accepted: 3 September 2002 / Published online: 17 December 2002 RID="*" ID="*"Corresponding author. Fax: +82-62/970-2204, E-mail: ytlee@kjist.ac.kr     

Incorporation behaviour of manganese in MBE grown Ga0.47In0.53As

Acceptor doping of MBE grown Ga_0.47In_0.53As on InP:Fe substrates utilizing manganese is investigated as an alternative for overcoming problems related to beryllium doping. The incorporation behaviour of manganese is analyzed in detail with respect to its application in optoelectronic device structures. Special emphasis is put on low-level and maximum-level doping relevant for use in buffer and contact layers, respectively. The dependence of activation energy and the degree of ionization on acceptor concentration is determined. At high doping levels the free-hole concentration is markedly lower than the doping concentration. It is attributed to the diffusion of acceptor species across the heterointerface into the substrate. Manganese diffusion is demonstrated to be an important effect for the interpretation of the measurement results. Manganese doping is applied in p⁺/n/p^–-layer structures for junction field effect transistor applications. The intended abruptness of acceptor profiles is deteriorated by diffusion of manganese in the Ga_0.47In_0.53As material. The degraded device characteristics obtained are attributed to the acceptor diffusion behaviour established.