Material-selective etching of InP and an InGaAsP alloy

Wet chemical etchants are inexpensive and can be employed easily in device fabrication. Material-selective etchants extend the design flexibility for devices with heterostructures. Several etchants on (100) InP and LPE-grown (100) InGaAsP are studied with emphasis on smooth crystal surfaces and well-defined mesa-structures by use of photoresist. The best results are obtained with the system glycerine: HCl HClO₄ for preferential attack of InP and with the system H₂O H₂SO₄ H₂O₂ for preferential etching of InGaAsP. Detailed information is given on the etching solutions investigated, on the etching conditions and the etching rates of the most useful etchants.     

Influence of temperature and optical confinement on threshold current of an InGaAs/InP quantum wire laser

In this paper, we investigate the influence of the temperature on gain and threshold current density of a V-groove quantum wire InGaAs/InP laser. The calculation shows that room-temperature operation can be achieved if the optical confinement is large enough (0.26% in our case), while its slight improvement above this limit (around 0.4%) can provide a significant reduction of the threshold current (more than 70%) and an improved temperature stability of the laser.     

Carrier-concentration dependence of velocity-field characteristics in ln0.53Ga0.47 as

The doping dependence of the velocity-field characteristic in InGaAs has been investigated by an analysis of measurements with transferred-electron devices. The electron peak velocity has been determined directly as a function of electron concentration and low-field mobility. The carrier-concentration dependence of the velocity-field characteristic has been deduced by comparing experimental and theoretical transient device behaviour. The experimental results support a theoretical approach for the velocity-field characteristic which has been proposed recently.     

Anelastic properties of aluminium thin films on silicon cantilevers

Thin films (thickness 40 to 250 nm) of Al on microstructurized Si substrates have been investigated by the vibrating-reed technique (typical frequencies 100 Hz to 10 kHz) with strain amplitudes in the range of 10⁻⁷ to 10⁻⁴ and for temperatures up to 850 K. The combined evaluation of flexural and torsional vibrations permits to separate the complex shear modulus and biaxial modulus of the thin layer, which helps to identify the damping mechanisms. For Al thin films with thickness <200 nm, in addition to the well-known damping peak due to grain boundary sliding (peak temperature about 370 K), a further maximum of damping has been observed around 600 K, the nature of which is discussed.     

Automatic counting of etch Pits in InP

A computer algorithm for automatic EPD-counting (etch-pit density) with an optical microscope is presented. Several dislocation etchants proposed in the literature to reveal structural defects on InP were employed and improved. Their reliability for automatic counting was proven. For a considerable number of samples exhibiting an EPD between 10⁴ and 10⁶ cm⁻² it is shown that the automatically counted number of etch pits agrees with the visually determined value within less than ±30%. Using a modified H₃PO₄:HBr etchant good results for automatically determined EPDs beyond 10⁷ cm⁻² were obtained on InP layers epitaxially grown on Si substrates.     

Mechanical spectroscopy of thin layers of PPV polymer on Si substrates

The vibrating reed technique with electro“static” excitation and optical detection has been applied to investigate thin layers of poly-phenylene-vinylene, deposited by spin coating onto microfabricated Si cantilevers, during temperature cycling programs between 90 and 540 K at a rate of 1 K/min. From the vibration frequencies the Young’s modulus of the film can be estimated to be about 10 MPa at room temperature in the precursor phase (if prepared from a solution in toluene), which increases by conversion to the conjugate bonded polymer to about 50 MPa. The temperature dependence of internal friction reveals the processes of γ relaxations (crankshaft motion of side branches in the precursor) and β-relaxation (movements of a few monomer blocks in the polymer chain), as well as peaks indicating the structural transformations during conversion, and possibly a glass transition in the amorphous precursor phase. After conversion only the β-relaxation persists.     

Transferred-electron effect in In0.53Ga0.47As

The transferred-electron effect in In0.53Ga0.47As is demonstrated by observation for the first time in the travelling-domain mode. Current pulses of more than 70% are found. From velocity/field characteristics the peak velocity is determined as (2.2 ± 0.3) × 107 cm/s. The temperature dependence of the peak current is measured.     

Transferred-electron effect in InGaAsP alloys lattice-matched to InP

Measurements of the transferred-electron effect in InP, In_0.73Ga_0.27As_0.64P_0.36, and in In_0.53Ga_0.47As are presented. The results show that especially InGaAs promises superior performance for high-efficiency Gunn devices. Important properties affecting the electron transfer have been investigated. The peak velocity v_p and its temperature dependence, the accompanying threshold field F_p, and the dependence of the current drop on the dimensions of the devices (nl and nd product) are reported. To demonstrate the potential of InGaAs first results with Gunn oscillators using devices of this alloy are mentioned.     

Microelectromechanical vibration sensor with optical interconnects

A resonant vibration sensor realized using silicon micromachining for wear monitoring of rotating machinery is described. It comprises a mechanical resonator, piezoresistive bridge, and components for fiber-optical signal readout by an infrared light-emitting diode. The performance of the microsystem is demonstrated by its static and dynamical behavior. The results confirm that the described sensor has the potential for on-line vibration control of rotating machinery operated under the conditions of industrial production