Properties of GaAs/InGaAs quantum-size structures containing δ〈Mn〉-doped layers

Properties of structures containing an InGaAs quantum well (QW) or InAs quantum dots (QDs) as well as δ〈C〉-and δ〈Mn〉-doped layers are investigated. Most of these structures are fabricated by the MOCVD epitaxy method; δ〈Mn〉-doped layers are obtained by low-temperature laser deposition directly in the epitaxial reactor. The structures under study exhibit three conduction channels: the δ〈C〉-doped layer, δ〈Mn〉-doped layer, and QW or wetting layer in the case of QDs. The contribution of each channel into the total conduction depend on the measurement temperature. Photoluminescence of the structures as a function of thickness of δ〈Mn〉-doped layer is studied.     

Injection electroluminescence from quantum-size InGaAs/GaAs structures with metal/semiconductor and metal-oxide-semiconductor junctions

Electroluminescence from forward-biased diode structures with Au(Ni)/GaAs and Au(Ni)/tunneling-thin oxide/GaAs junctions has been studied. The possibility of luminescence amplification from the Schottky diodes by introducing a tunneling-thin anode-oxide or heavily doped p ⁺-GaAs layer between the metal and semiconductor have been demonstrated. The studies of the temperature dependence of electroluminescence and the I-W curves indicate that the amplification of the electroluminescence intensity from the above structures may be associated with lowering the potential barrier for the minority carriers under the forward bias of the Schottky barrier.     

Strained germanium films in Ge/InGaAs/GaAs heterostructures: Formation of edge misfit dislocations at the Ge/InGaAs interface

Heterostructures of the “strained Ge film/artificial InGaAs layer/GaAs substrate” type have been grown by molecular beam epitaxy. A specific feature of these structures is that the plastically relaxed (buffer) InGaAs layer has the density of threading dislocations on a level of 10⁵–10⁶ cm⁻². These dislocations penetrate into the strained Ge layer to become sources of both 60° and 90° (edge) misfit dislocations (MDs). Using the transmission electron microscopy, both MD types have been found at the Ge/InGaAs interface. It has been shown that the presence of threading dislocations inherited from the buffer layer in a tensile-strained Ge film favors the formation of edge dislocations at the Ge/InGaAs interface even in the case of small elastic deformations in the strained film. Possible mechanisms of the formation of edge MDs have been considered, including (i) accidental collision of complementary parallel 60° MDs propagating in the mirror-tilted {111} planes, (ii) induced nucleation of a second 60° MD and its interaction with the primary 60° MD, and (iii) interaction of two complementary MDs after a cross-slip of one of them. Calculations have demonstrated that a critical layer thickness (h _c ) for the appearance of edge MDs is considerably smaller than h _c for 60° MDs.     

Excitation energy dependence of the optical properties of InGaAs/GaAs quantum well heterostructures

Il Nuovo Cimento D - We report an experimental study on a large set of InGaAs/GaAs quantum well structures by means of continuous-wave photoluminescence and photoluminescence excitation. The...     

Dependence of the heavy-hole exciton reduced mass on quantum-well size in InGaAs/GaAs heterostructures

We present low temperature photoluminescence investigations of the exciton ground state of In_0.14Ga_0.86As/GaAs quantum wells (QW) in the presence of pulsed magnetic fields up to 50 T. The exciton in-plane reduced mass and the heavy-hole in-plane mass are determined from the best fit of theoretical calculations to the magnetic field dependence of PL peaks. When the QW thickness decreases, their masses increases due to valence-band mixing effect.     

Effect of hydrogen on modulation-doped AlGaAs/InGaAs/GaAs heterostructures: a photoluminescence study

The effect of hydrogen on donors and interface defects in silicon modulation doped Al_xGa_1−xAs/In_yGa_1−yAs/GaAs heterostructures has been investigated by photoluminescence (PL). Hydrogenation was carried out on two sets of samples, one set consists of high quality pseudomorphic heterostructures and another set having partially lattice relaxed structures prone to the defects. On exposure of high quality pseudomorphic structures to hydrogen plasma above 150 °C, a significant blue shift in the PL peak positions as well as bandwidth narrowing is observed. This indicates, the reduction in two-dimensional electron gas in the In_yGa_1−yAs quantum well due to hydrogen passivation of silicon donors in the Al_xGa_1−xAs supply layer. The reactivation of the donors is observed upon annealing the hydrogenated sample for 1 h at 250 °C under hydrogen ambient. Another interesting feature is a significant improvement in the PL of lattice-relaxed structures upon hydrogenation of the samples above 250 °C, which is attributed to the hydrogen passivation of interface defects due to the misfit dislocations.     

Formation of spin light-emitting diodes based on InGaAs/GaAs heterostructures containing ferromagnetic inclusions

The electroluminescence of light-emitting diodes based on heterostructures with InGaAs quantum wells and a delta 〈Mn〉 doped layer in the GaAs barrier is studied. It is shown that the diodes emit circularly polarized light with the degree of polarization depending on the applied magnetic field and on temperature. We assume that the temperature dependences of the degree of polarization are determined by a change in the mutual position of energy levels of Mn ions in the delta layer and of holes in a quantum well.     

Catastrophic degradation of pulsed lasers based on AlGaAs/InGaAs/GaAs heterostructures with electron-beam pumping

Catastrophic degradation of pulsed lasers based on InGaAs/AlGaAs/GaAs structures with different design of the active domain with transverse pumping by the electron beam at T = 300 K is studied. In lasers based on structures with a InGaAs single quantum well and with seven quantum wells, the maximal values of pulsed power are 70–90 and 10–20 W, respectively.     

Emitting heterostructures with a bilayer InGaAs/GaAsSb/GaAs quantum well and a GaMnAs ferromagnetic layer

The radiative and magnetic properties of novel heterostructures with a bilayer InGaAs/GaAsSb/GaAs quantum well and a GaMnAs ferromagnetic layer are studied. The circular polarization of electroluminescent radiation is observed at temperatures from 10 to 160 K. The magnetic field dependences of the degree of circular polarization are nonlinear with a hysteresis loop at temperatures from 10 to 50 K, and they become linear at higher temperatures. The magnitude of polarization at the saturation magnetization of GaMnAs in the 2000 Oe field remains at the level of ~0.2%.     

Combined cross-sectional STM/AFM in liquid: Study of InGaAs/GaAs heterostructures with quantum wells and dots

Combined scanning tunneling and atomic force microscopy (STM/AFM) of cross-sectional cleavages in a protective liquid medium (oil) is applied to study InGaAs/GaAs heterostructures with quantum wells and dots. It is shown that the quantum wells and dots can be visualized on cleavages in both AFM and STM modes and to measure the current-voltage characteristics of the contact between an AFM probe and the cleavage surface.     

Temperature dependence of the circular polarization of electroluminescence from spin-polarized light-emitting diodes based on InGaAs/GaAs heterostructures

The temperature dependence of the circular polarization degree of the electroluminescence from light-emitting diodes based on InGaAs/GaAs-quantum-well (QW) heterostructures with a closely located ferromagnetic Mn δ layer is investigated. It is found that the Mn δ layer ferromagnetically affects holes in the QW. This effect is characterized by spin polarization of the holes and the appearance of circularly polarized emission components under electroluminescence conditions. It is demonstrated that the ferromagnetic properties of a δ layer can be studied by analyzing the QW luminescence. The Curie temperatures of the ferromagnetic system are determined using the results of investigations.     

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.     

Impurity cyclotron resonance in InGaAs/GaAs superlattice and InGaAs/AlAs superlattice grown on GaAs substrates

Various temperature measurements of cyclotron resonance (CR) under pulsed ultra-high magnetic field up to 160 T were carried out in InGaAs/GaAs superlattice (SL) and InGaAs/AlAs SL samples grown by molecular beam epitaxy on GaAs substrates. Clear free-electron CR and impurity CR signals were observed in transmission of CO₂ laser with wavelength of 10.6 μm. A binding energy of impurities in these SLs was roughly estimated based on the experiment as result, and we found it was smaller than the previous experimental result of GaAs/AlAs SLs and theoretical calculation with a simple model.     

Infrared radiation from hot holes during spatial transport in selectively doped InGaAs/GaAs heterostructures with quantum wells

The infrared radiation from hot holes in In_xGa_1−x As/GaAs heterostructures with strained quantum wells during lateral transport is investigated experimentally. It is found that the infrared radiation intensities are nonmonotonic functions of the electric field. This behavior is due to the escape of hot holes from quantum wells in the GaAs barrier layers. A new mechanism for producing a population inversion in these structures is proposed. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 7, 478–482 (10 October 1996)     

Quantum point contacts on InGaAs/InP heterostructures

For the first time we have observed quantized conductance in a split gate quantum point contact prepared in a strained In_0.77Ga_0.23As/InP two-dimensional electron gas (2DEG). Although quantization effects in gated two-dimensional semiconductor structures are theoretically well known and proven in various experiments on AlGaAs/GaAs and also on In_0.04Ga_0.96As/GaAs, no quantum point contact has been presented in the InGaAs/InP material with an indium fraction as high as 77% so far. The major problem is the comparatively low Schottky barrier of the InGaAs (φ_B≈ 0.2 eV) making leakage-free gate structures difficult to obtain. Nevertheless this heterostructure—especially with the highest possible indium content—has remarkable properties concerning quantum interference devices and semiconductor/superconductor hybrid devices because of its large phase coherence length and the small depletion zone, respectively. In order to produce leakage-free split gate point contacts the samples were covered with an insulating SiO₂layer prior to metal deposition. The gate geometry was defined by electron-beam lithography. In this paper we present first measurements of a point contact on an In_0.77Ga_0.23As/InP 2DEG clearly showing quantized conductance.