InAs/AlSb quantum cascade lasers operating at 6.7 /spl mu/m

Quantum cascade lasers based on the InAs/AlSb material system have been realised. The optical confinement is obtained using a plasmon waveguide with n/sup +/-InAs cladding layers. In pulse mode the lasers emit close to 6.7 /spl mu/m with a threshold current density of 5 kA/cm/sup 2/ at 90 K. The maximum operating temperature is 220 K.     

Current and temperature tuning of quantum-well lasers operating in 2.0-to 2.4-µm range

Radiation spectra of GaInAsSb/GaAlAsSb-based quantum-well diode lasers in pulsed and quasi-continuous operation modes were studied in the temperatures range from −10 to +20°C with driving currents varying from 50 to 200 mA. For currents exceeding the threshold value by no more than 30%, a single-mode lasing was usually observed. A further increase in current leads, as a rule, to the appearance of 3–5 additional long-wavelength cavity modes, which suggests the growth of gain in this spectral range due to the interaction of modes. In single-mode conditions, the lasing wavelength is red-shifted with temperature at a rate of 2–3 ?/K because of the current-induced heating of the laser and the corresponding increase in the refractive index. The rate of this heating is estimated at 0.1 μs. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 4, 2003, pp. 502–507. Original Russian Text Copyright ? 2003 by Astakhova, Baranov, Viset, Imenkov, Kolchanova, Stoyanov, Chernyaev, Yarekha, Yakovlev.     

The formation of natural oxide on the mirrors of GaSb/GaInAsSb/GaAlAsSb laser heterostructures at places of emergence of al-rich layers

Formation of a natural oxide in ambient atmosphere of the mirrors of a GaSb/GaInAsSb/Ga_0.1Al_0.9As_0.93Sb_0.07 laser heterostructure at places of emergence Al-rich layers on the mirror surface is studied. The evolution of topography of the laser mirrors produced by cleavage under ambient and ultrahigh vacuum conditions was studied by AFM and STM for mirrors cleaved. The oxidation of Ga_0.1Al_0.9As_0.93Sb_0.07 layers on the mirror surface was monitored for more than a year. It is shown that the oxide layer develops over the course of several months and then attains a constant thickness of about 1 μm. In the course of natural oxidation, the volume of the oxide layer increases, which results in its protrusion above the laser mirror surface approximately by a third of the total thickness of the oxide formed. Ultrahigh vacuum studies ruled out the previously assumed occurrence of the effect of plastic extension of Al-rich layers at the instant of cleavage and the resulting protrusion over the cleavage plane. At the initial stage of oxidation, the oxide protruding above the surface demonstrates an unusual concave region in the upper part, which disappears as the oxide grows further. An explanation of the observed transformation of the shape of the oxide layer is offered. It is assumed that the chemical composition of the oxide varies as its thickness increases.     

Continuous-wave operation of quantum cascade laser emitting near 5.6 /spl mu/m

Buried heterostructure quantum cascade lasers emitting at 5.64 /spl mu/m are presented. Continuous-wave (CW) operation has been achieved at -30/spl deg/C for junction down mounted devices with both facets coated. A 750 /spl mu/m-long laser exhibited 3 mW of CW power with a threshold current density of 5.4 kA/cm/sup 2/.     

Comparative study of erbium disilicide thin films grown in situ under ultrahigh vacuum or ex situ with a capping layer

Erbium disilicide (ErSi_2-x) thin films grown by two different techniques are compared using a variety of characterization techniques, both electrical and physical. The first technique involves Er deposition and annealing under ultrahigh vacuum and the second one focuses on Ti/Er/Si(100) stacks evaporated under high vacuum and heated ex situ by rapid thermal annealing. Crystalline phase identification by X-ray diffraction reveals the formation of ErSi_2-x for all the studied samples. Cross-sectional transmission electron microscopy shows that the Ti cap transforms into Ti-Si compounds. The efficient stripping of the capping layer is also demonstrated. Atomic force microscopy evidences the formation of inverted pyramidal defects in both cases, with some improvement for the Ti-capped samples. X-ray photoelectron spectroscopy depth profiles show that the ErSi_2-x films and the ErSi_2-x/Si interfaces are oxygen-free. The extracted Schottky barrier height of ErSi_2-x/n-Si contacts lies around 0.3 eV notwithstanding the annealing temperature or the growth technique. It thus demonstrates a route to form ErSi_2-x thin films that advantageously compares with reference ultrahigh vacuum samples with less stringent fabrication conditions.