This study is based on two commercially available YBCO thin films deposited by the thermal coevaporation method on different substrates (MgO and LaAlO3). Those films should be optimized for microwave applications. The structure and microstructure of the film deposited on LaAlO3 have been investigated, respectively by XRD and SEM. These characterizations showed the high quality of the films concerning the c-axis orientation and the smooth and homogenous morphology. The films have then been etched into two different coplanar line resonators by ionic method (YBCO/LaAlO3) and chemical one (YBCO/MgO) and their microwave properties have been characterized in two different cryogenic experimental set-ups. Despite the differences between these coplanar resonators, we have obtained the same intrinsic parameters (λ0 = 190 nm, T c=87 K with γ = 3) corresponding to the data provided by THEVA and a very low surface resistance (R s=0.4 m Ω at 31 K and 10 GHz).

This paper deals with the determination of lambda and Z(8) of YBa2Cu3O7-delta thin films deposited on MgO single-crystals, from 36 GHz resonant conical cavity measurements performed in the 25 K to 300 K temperature range. The results are discussed in relation with DC electrical transport properties of the films and also with substrate preparation prior to YBaCuO deposition.

Two characterisations methods in microwaves are presented. They permit to obtain sigma*, Rs and lambda for a HTS film without the need of any theoretical model for the superconductivity. The best film tested exhibits at 35GHz and 78K a Rs value of 10m Omega, at least three times lower than the copper one. A quasi-integrated oscillator has been realised on a 1cm(2) area: it oscillates at 12GHz and close to liquid nitrogen temperature. At lower temperatures an output power of +3dBm and a phase noise of -100dBc/Hz at 100kHz from the carrier have been recorded.

Low temperature behaviour of InGaAsP laser diode is studied. The laser is a Fabry-Perot type with a Buried Heterostructure. A large improvement of threshold current is obtained as the temperature decreases. The exponential variation of Ith is verified and a T0 value of 69K is deduced. The intrinsic resonant frequency is measured with noise analysis. This resonance varies as the square root of the net injected current. The slopes of these curves are found to increase dramatically with decreasing temperature. The 3 dB bandwidth experiments are also performed, leading in the same way, to a large increase of the slopes with cooling but package parasitics limit the maximum achievable bandwidth. The influence of the laser parasitics, such as the roll-off phenomenum, is also underlined.

A fixture is presented that accepts both nounal and superconducting microstrip structures for S-parameter measurements. The use of small replaceable inserts and a compression contact for the strip makes the fixture especially suited for rapid prototype testing of microstrip circuits. The technique is explained and measurements at room temperature and at low temperatures are demonstrated.

A microwave measurement technique, using a novel cell which enables the sheet resistance (R⧠), the carrier density (n), and the mobility (μ) of epitaxial layers to be measured, is proposed. The system, controlled by a microcomputer, performs this characterization by measuring galvanomagnetic effects. The sample is only lightly pressed on the cell. The electrical contacts between the sample and the cell are capacitive. This method is thus nondestructive and requires no technological process. The data treatment necessitates knowledge of factors which are determined from a calibration procedure made only once. For the GaAs samples reported here, the accuracy is better than 5% for R⧠, 15% for μ, and 20% for n.

We propose a microwave device using a novel cell which allows one to measure the sheet resistance (Rn), the carrier density (n) and the mobility (¿) of epitaxial layers. The electrical contacts between the sample and the cell are capacitive. The method is non-destructive and doesn't require any technological process. Measurements can be performed within the following ranges : 5 ¿ ≪ R ≪ 2500 ¿; 100 cm2/V.s. ≪ ¿ ; 5 1015cm¿3 ≪ n ≪ 5 1018 cm¿3