Lasing properties of strain-compensated InAs/InGaAsN/GaAsN heterostructures in 1.3–1.55 μm spectral range

We have studied the radiative properties of heterostructures comprising InAs/InGaAsN quantum wells in strain-compensated GaAsN/InGaAsN superlattices, which are intended for the active regions of lasers operating at 1.3–1.55 μm. Using such superlattices and additional InAs monolayer insertions, it is possible to control the wavelength of room-temperature emission from InGaAsN quantum wells within 1.3–1.55 μm. The InAs/InGaAsN/GaAsN laser heterostructures are obtained, whose laser generation spectrum at 85 K corresponds to room-temperature lasing at ～1.5 μm.     

Molecular beam epitaxy growth methods of wavelength control for InAs/(In)GaAsN/GaAs heterostructures

We discuss the molecular beam epitaxy (MBE) growth methods of emission wavelength control and property investigations for different types of InAs/(In)GaAsN/GaAs heterostructures containing InGaAsN quantum-size layers: (1) InGaAsN quantum wells deposited by the conventional mode in a GaAs matrix, (2) InAs quantum dots deposited in a GaAsN matrix or covered by an InGaAs(N) layer, and (3) InAs/InGaAsN/GaAsN strain-compensated superlattices with quantum wells and quantum dots. The structures under investigation have demonstrated photoluminescence emission in a wavelength range of ～1.3-1.8?μm at room temperature without essential deterioration of the radiative properties.     

Effect of structural design on the optical properties of strain-compensated InAs/InGaAsN/GaAsN superlattices

We have studied the influence of structural design on the optical properties of heterostructures comprising InAs quantum wells (QWs) and quantum dots (QDs) in strain-compensated GaAsN/InGaAsN superlattices. It is established that, using such superlattices with various QW and barrier thicknesses and different numbers (from one to three) InAs inserts in the active region, it is possible to control the wavelength of room-temperature emission within 1.3–1.76 μ m without deteriorating the output radiation characteristics.     

Emission characteristics improvement in structures with InAs/GaAsN/InGaAsN superlattices

The influence of some parameters of nitrogen-containing heterostructures InAs/GaAsN/InGaAsN with strain-compensated superlattices (SCSL) on their emission characteristics has been studied. It is established that the net strain in the structure affects the photoluminescence (PL) linewidth, internal quantum efficiency, intensity, and wavelength. The maximum PL intensity and minimum full width at half maximum (FWHM) of the PL line were achieved with small strains (0–0.2%), whereas the maximum wavelengths (∼1.76 μm) observed for large strain (about +1%). By adding multilayer InAs inserts in the active InGaAsN quantum well in combination with using strain-compensated GaAsN/InGaAsN superlattices, it is possible to control the room-temperature emission wavelength in the range of 1.45–1.76 μm without significantly deteriorating the emissiion characteristics.     

Room-temperature photoluminescence at 1.55 μm from heterostructures with InAs/InGaAsN quantum dots on GaAs substrates

Room-temperature photoluminescence (PL) at 1.55 μm from heterostructures with InAs/InGaAsN quantum dots (QDs) grown by MBE on GaAs substrates is demonstrated for the first time. The effect of nitrogen incorporated into InAs/InGaAsN QDs on the PL wavelength and intensity was studied. The integral intensity of PL from the new structure with InAs/(In)GaAsN QDs is comparable to that from a structure with InGaAsN quantum wells emitting at 1.3 μm.     

Long-wavelength emission in InGaAsN/GaAs heterostructures with quantum wells

The properties of InGaAsN/GaAs heterostructures with quantum wells on GaAs substrates were studied. The GaAsN layers containing InGaAsN quantum wells with a high (exceeding 1%) nitrogen concentration were obtained. The long-wavelength emission in the InGaAsN quantum wells is obtained in the wavelength range up to 1.32 μm at room temperature. The effect of the InGaAsN quantum parameters on the optical properties of heterostructures is studied.     

Electroluminescence of quantum-well structures on type-II InAs/GaSb heterojunctions

The electroluminescent properties of quantum-well diode structures on staggered type-II heterojunctions in the InAs/GaSb system, obtained by molecular-beam epitaxy on InAs substrates, are investigated. Electroluminescence is observed in the spectral range 3–4 μm at T=77 K. It is found that emission bands due to recombination transitions involving electrons from the size-quantization levels of both the self-matched quantum wells at the InAs/GaSb type-II heterojunction and of the square quantum wells in short-period superlattices. Pis’ma Zh. Tekh. Fiz. 24, 50–56 (June 26, 1998)     

InAs/GaAs lasers with very thin active layer

InAs/GaAs laser structures based on atomically thin InAs strained quantum wells were prepared by metal–organic vapour phase epitaxy. The dependence of electroluminescence spectra on the thickness, as well as on the number of InAs quantum wells, was studied. The temperature dependence of the mode structure and optical output power were studied in the range from 25 to 100°C. The position of laser emission can be shifted by changing the thickness and the number of InAs active layers from 1.15 to 1.4 eV. Wavelength switching with increasing operating temperature and excitation current was observed.     

MOCVD 生长及 TEM 表征 GaAs/Al_xGa_(1-x)As 量子异质结构材料

本文报道 MOCVD 生长 GaAs/Al_xGa_(1-x)As 量子异质结构材料(超晶格、量子阱及量子共振隧穿二极管),采用横断面透射显微术表征了样品的界面结构。实验表明:多量子阱与超晶格的周期性良好,层与层之间界面清晰,采用[100]带轴入射,观察到超晶格的 TEM 卫星衍射斑,测量到量子阱中电子的子能级跃迁吸收。研究了生长工艺和材料结构的关系,分析了影响 RT 器件的因素。     

Determination of indium and nitrogen contents of InGaAsN quantum wells by HRXRD study supported by BAC calculation of the measured energy gap

Determination of indium and nitrogen content in InGaAsN quantum wells (QWs) is often based on the analysis of high-resolution X-ray diffraction (HRXRD) measurements. The comparison of diffraction curves of two similar samples, with and without nitrogen, together with an assumption of constant indium incorporation efficiency during the growth of layers with and without nitrogen, may lead to a large deviation in the determined In and N content. The HRXRD curve simulations supported by bandgap determination and calculations seem to be a solution of this problem. Comparison of the results achieved from simulated HRXRD curves with the calculations of all QWs transitions measured by contactless electro-reflectance (CER) can lead to reduction of deviations in composition determination of InGaAsN quantum wells. The proposed algorithm was applied for investigation of InGaAsN QWs grown by atmospheric pressure metalorganic vapor phase epitaxy (APMOVPE).     

InAs/GaAs nanostructures grown on patterned Si(001) by molecular beam epitaxy

The potential benefit from the combination of the optoelectronic and electronic functionality of III-V semiconductors with silicon technology is one of the most desired outcomes to date. Here we have systematically investigated the optical properties of InAs quantum structure embedded in GaAs grown on patterned sub-micron and nanosize holes on Si(001). III-V material tends to accumulate in the patterned sub-micron holes and a material depletion region is observed around holes when GaAs/InAs/GaAs is deposited directly on patterned Si(001). By use of a 60?nm SiO(2) layer and patterning sub-micron and nanosize holes through the oxide layer to the substrate, we demonstrate that high optical quality InAs nanostructures, both quantum dots and quantum wells, formed by a two-monolayer InAs layer embedded in GaAs can be epitaxially grown on Si(001). We also report the power-dependent and temperature-dependent photoluminescence spectra of these structures. The results show that hole diameter (sub-micron versus nanosize) has a strong effect on the structural and optical properties of GaAs/InAs/GaAs nanostructures.     

Carrier loss mechanisms in type II quantum wells for the active region of GaSb-based mid-infrared interband cascade lasers

Thermal quenching of photoluminescence has been measured for InAs/GaInSb broken gap system quantum wells as a function of the thickness of the conduction and valence band wells. The primary activation energy appears too small for the electrons to leave the well, and insensitive to even significant changes in the InAs layer thickness and hence electron confinement potential. On the contrary, it varies strongly with the modification of the confinement of holes in the GaInSb layer. Thus, tunneling-assisted escape of holes into the GaSb layers has been recognized as the dominant carrier loss mechanism in these type II quantum wells.     

Metamorphic InAs/InGaAs/InAlAs quantum wells with submonolayer InSb insertions emitted in the mid-infrared spectral range

Metamorphic InAs/InGaAs/InAlAs quantum wells with submonolayer InSb insertions have been grown for the first time by molecular beam epitaxy on GaAs (001) substrates using a graded InAlAs buffer layer with increasing In composition. The given nanoheterostructures demonstrate an intense photoluminescence at a wavelength of over of over 3 μm (80 K), which is shifted toward longer wavelengths as compared with that of the structures without InSb insertions.     

Atomic scale interface engineering for strain compensated epitaxially grown InAs/AlSb superlattices

This paper presents a systematic investigation of strain compensation schemes for InAs/AlSb superlattices (SLs) on GaSb substrates. Short growth interruptions (soak times) under varying arsenic and/or antimony beam equivalent pressures in InAs/AlSb SLs with exemplary dimensions of about ((2.4/2.4) ± 0.2) nm were investigated to achieve strain compensation. When using uncracked As(4), strain compensation was found to be unaccomplishable unless sub-monolayer AlAs spikes were inserted at the InAs → AlSb interface. In contrast, the supply of cracked As(2) dimers leads directly to the formation of strain compensating AlAs-like interfaces. This mechanism allows various growth sequences for strain compensated superlattices, including soak-time-free and Sb-soak-only SL growth. Each of the two latter approaches yields layers with excellent crystal quality and minimal intermixing at the heterointerfaces as verified by high resolution x-ray diffraction analysis and transmission electron microscopy.     

InAs/GaSb superlattices fabricated by metalorganic chemical vapor deposition

The possibility of fabricating InAs/GaSb strained-layer superlattices by metalorganic chemical vapor deposition has been experimentally demonstrated. The results of transmission electron microscopy and photoluminescence spectroscopy investigations showed that the obtained structures comprise an InAs?GaSb superlattice on a GaSb substrate consisting of 2-nm-thick InAs and 3.3-nm-thick GaSb layers.

     

GaAsN/GaAs and InGaAsN/GaAs heterostructures grown by molecular beam epitaxy

Molecular beam epitaxy was used to fabricate GaAsN/GaAs and InGaAsN/GaAs heterostructures, and the influence of the growth regimes on their characteristics was studied. It is shown that implantation of nitrogen causes a substantial long-wavelength shift of the radiation. The possibility of obtaining 1.4 μm radiation at room temperature was demonstrated using In_0.28Ga_0.72As_0.97N_0.03/GaAs quantum wells. Pis’ma Zh. Tekh. Fiz. 24, 81–87 (December 12, 1998)     

Scanning gate imaging of quantum dots in 1D ultra-thin InAs/InP nanowires

We use a scanning gate microscope (SGM) to characterize one-dimensional ultra-thin (diameter ≈ 30 nm) InAs/InP heterostructure nanowires containing a nominally 300 nm long InAs quantum dot defined by two InP tunnel barriers. Measurements of Coulomb blockade conductance versus backgate voltage with no tip present are difficult to decipher. Using the SGM tip as a charged movable gate, we are able to identify three quantum dots along the nanowire: the grown-in quantum dot and an additional quantum dot near each metal lead. The SGM conductance images are used to disentangle information about individual quantum dots and then to characterize each quantum dot using spatially resolved energy-level spectroscopy.     

Optical properties of self-assembled lateral superlattices in AlInAs epitaxial layers and AlAs/InAs short-period superlattices

Characterization of self-assembled lateral superlattices in AlInAs epitaxial layers and AlAs/InAs short-period superlattices is presented. These structures are spontaneously generated during the epitaxial growth by metal–organic chemical vapor deposition and molecular beam epitaxy. Transmission electron microscopy reveals the structural details and electro-modulated reflectance is used to characterize the energy and anisotropy of the optical transitions in the lateral superlattices. We demonstrate several properties of these self-assembled structures: (a) the band gap energy can be changed by as much as 350 meV, (b) the polarization anisotropy of the lowest energy transition exceeds 90%, (c) the superlattice axis and the direction of the optical anisotropy can be oriented along two non-equivalent directions in the plane of the substrate, and (d) the valence band splitting between heavy- and light-hole transitions is significant. We discuss the difference between the samples from the two growth techniques. Finally, we theoretically model the electronic states in these lateral superlattices and we demonstrate that the difference in average InAs composition between the well and barrier can be as high as 35%.     

自组织InAs/GaAs与InGaAs/GaAs量子点生长及退火情况的比较

本文采用MBE进行InAs/GaAs与InGaAs/GaAs量子点的生长,利用RHEED进行实时监测,并利用RHEED强度振荡测量生长速率。对生长的InAs/GaAs和InGaAs/GaAs两种量子点生长过程与退火情况进行对比,观察到当RHEED衍射图像由条纹状变为网格斑点时,InAs所需要的时间远小于InGaAs;高温退火下RHEED衍射图像恢复到条纹状所需要的时间InAs比InGaAs要长。     

InAs/GaInSb应变层超晶格材料的界面结构

介绍了InAs／GaInSb应变层超晶格材料的界面结合类型及其对材料界面结构和光电性能的影响,分析了在超晶格界面处的原子置换和扩散现象。同时,总结了分子束外延生长过程中控制InAs／GaInSb超晶格界面结构的生长工艺,指出采用原子迁移增强（MEE）外延生长技术,可以有效地抑制界面处原子的置换和扩散现象。