[en] In this work, the design and implementation of Sb-free short wavelength strain-compensated quantum cascade lasers in the 3–4 μm spectral range is presented. Due to the presence of highly strained AlAs-barrier layers, the optimization of the epitaxial growth process is firstly discussed. The used active region design is then presented together with the observed laser performance. Watt-level room temperature emission at 3.3 μm is shown for Fabry–Perot devices and laser operation in pulsed mode is observed above 350 K. The laser performance is comparable with Sb-containing quantum cascade lasers. Spectral tuning of the lasers in an external cavity configuration over more than 275 cm⁻¹ is achieved with an emission wavelength as short as 3.15 μm. For the first time in this spectral range, results on single-mode buried heterostructure distributed feedback lasers are shown. (paper)

[en] We demonstrate a hole double quantum dot in an undoped GaAs/AlGaAs heterostructure. The interdot coupling can be tuned over a wide range, from formation of a large single dot to two well-isolated quantum dots. Using charge sensing, we show the ability to completely empty the dot of holes and control the charge occupation in the few-hole regime. The device should allow for control of individual hole spins in single and double quantum dots in GaAs

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[en] The pulse operation of two DEF GaAs junction lasers employing the fundamental grating order at 77⁰K for double-heterostructures formed by both liquid and vapor phase epitaxy is described

[en] The semiconductor injection laser includes a thin inner GaAs p-n junction layer between two outer GaAlAs layers which are backed by further thin outer GaAlAs layers with a heavier doping of AlAs. This reduces optical losses. Optical energy is further confined within the inner layers and the lasing threshold reduced by added outer GaAs layers of low electrical and thermal resistivity

[en] It is necessary to protect the surface of AlAs-based heterostructures from oxidation using a GaAs cap layer because of the high reactivity of aluminum. Thus, the surface region of these heterostructures always contains a GaAs/AlAs heterojunction. Here, it is demonstrated that, under nonresonant photoexcitation, the photoluminescence spectrum of AlAs-based heterostructures features a band associated with this heterojunction. The intensity of this band is determined by the thickness and doping type of the GaAs cap layer.

[en] The self-consistent pseudopotential method has been applied to describe the electronic structure of the abrupt (110) interfaces of AlAs--GaAs, Ge--GaAs, and Ge--ZnSe system. These systems were chosen both for their technological interest as well as to study trends with ionicity. The method allows the study of existence, character, and density of interface states as well as allowing estimates of the conduction and valence-band discontinuities and the characterization of the bonding properties of the interface. The results indicate that the ideal structure may be stable for AlAs--GaAs, but the character of the bonds at the Ge--GaAs and Ge--ZnSe interfaces suggest unbalanced forces on the atoms which will lead to relaxation. It is suggested that, in addition to the change of ionicity, the change of crystal symmetry (diamond--zincblende) across the interface may be of central importance in these systems

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[en] We report on first-principles calculations of spin-dependent quantum transport in a CrAs(0 0 1)/AlAs(0 0 1) heterogeneous junction and predict a strong diode effect of charge and spin current. The minority spin current is absolutely inhibited when the bias voltage is applied to the terminals of both CrAs and AlAs. The majority spin current is inhibited when the bias voltage is applied to the terminal of CrAs and 'relaxed' when the bias voltage is applied to the terminal of AlAs. The charge and spin current diode are promising for reprogrammable logic applications in the field of spintronics