Marcin Myśliwiec

Proton implantation for the isolation of AlGaAs/GaAs quantum cascade lasers

The novel fabrication scheme of the mid-infrared (~9.5 μm) Al0.45Ga0.55As/GaAs plasmon-enhanced-waveguide quantum cascade laser (QCL) is reported. The electric isolation was made exclusively by 6.5 μm-deep proton implantation. The applied implantation allowed us to suppress the current spreading and at the same time enabled the laser radiation confinement without any mesa formation. A galvanic gold layer at least 3.5 μm thick covering the top ohmic contact was used as a mask for implantation. This mask was not removed after the implantation, but it served for heat spreading from the laser. A considerable reduction in the necessary technological steps was obtained with the presented novel fabrication scheme, in comparison with the standard mesa-etching-based method.

Thermal and mechanical properties of sintered Ag layers for power module assembly

Purpose – The purpose of our paper is to investigate thermal and mechanical properties of Ag sintered layers used for assembly of SiC diode to Direct Bonding Copper (DBC) interposer. How SiC devices are assembled to ceramic package defines efficiency of heat transfer and mechanical support. Design/methodology/approach – Ag microparticles, sized 2-4 μm and flake shaped, were used as joining material. The parameters of sintering process were as follows: temperature 400°C, pressure 10 MPa and time 40 min. It was found that after sintering and long-term aging in air at 350°C the adhesion is in the range of 10 MPa, which is enough from a practical point of view. The thermal properties of the SiC die assembled into a ceramic package were also investigated. In the first step, the calibration of the temperature-sensitive parameter VF (IF = 2 mA) was done and the relation between VF and temperature was found. In the next step, the thermal resistance between junction and case was determined knowing junction and cas...

Application of direct bonded copper substrates for prototyping of power electronic modules

Purpose – This paper aims to present certain issues in direct bonded copper (DBC) technology towards the manufacture of Al2O3 or AlN ceramic substrates with one or both sides clad with a copper (Cu) layer. Design/methodology/approach – As part of the experimental work, attempts were made to produce patterns printed onto DBC substrates based on four substantially different technologies: precise cutting with a diamond saw, photolithography, the use of a milling cutter (LPKF ProtoMat 93s) and laser ablation with differential chemical etching of the Cu layer. Findings – The use of photolithography and etching technology in the case of boards clad with a 0.2-mm-thick Cu layer, can produce conductive paths with a width of 0.4 mm while maintaining a distance of 0.4 mm between the paths, and in the case of boards clad with a 0.3-mm-thick copper layer, conductive paths with a width of 0.5 mm while maintaining a distance of 0.5 mm between paths. The application of laser ablation at the final step of removing the un...

Challenges in packaging of IR detectors - technology of elastic electrical connections

This paper describes the study on flexible connections application in IR detector package. Such a connection is used between two modules in single package. One module is IR detector operating at -73 °C, other is electronic controlling circuit operating at room temperature. Flexible electrical connection must provide good electrical parameters in both DC and RF regime as well as poor thermal conductivity. 35 μm epoxy-phenolic foil with 5 μm Ni film and special RF compatible Ground-Signal-Ground geometry was successfully applied as connection. Low eutectic temperature InSn solder was used for soldering flexible connection to both IR detector and electronic circuit. Two types of soldering processes were investigated: bump and lap type. Flexible connection was tested for DC operation with long term stability test and RF parameters were determined. Authors found that both joining techniques are suitable for application in IR photodetector devices. However lap type joint is easier to apply in technological process, therefore it will be applied in final assembly.

Material and technological aspects of high-temperature SiC device packages reliability

Purpose – The purpose of this paper is to deal with material and technological aspects of SiC diodes assembly in ceramic packages. The usefulness of combinations of different materials and assembly techniques for the creation of inner connection system in the ceramic package, as well as the formation of outer connections able to work at temperatures up to 350°C, were evaluated. Design/methodology/approach – The ceramic package consists of direct bonded copper (DBC) substrate with Cu pads electroplated by Ni or Ni/Au layers on which a SiC diode was assembled by sintering process using Ag microparticles. For the connections inside the ceramic package, the authors used Al/Ni and Au-Au material system based on aluminium or gold wire bonding. The authors sealed the ceramic package with glass encapsulation and achieved a full encapsulation. Outer connections were manufactured using Cu ribbon plated with Ag layer and sintered to DBC by Ag micro particle. The authors investigated the long-term stability of electr...

Tuning properties of long-period gratings by atomic layer deposited zinc oxide nano-coating

This work presents an application of thin zinc oxide (ZnO) films obtained using atomic layer deposition (ALD) for effective tuning of spectral response and the refractive-index (RI) sensitivity of long-period gratings (LPGs). The technique allows for an efficient and well controlled deposition at monolayer level of excellent quality nano-films as required for optical sensors. The effect of ZnO deposition on spectral properties of the LPGs is discussed. We correlated the increase in ZnO thickness with the shift of the LPG resonance wavelength and proved that similar films are deposited on fibers and silicon reference samples in the same process run. The thin overlay effectively changes the distribution of the cladding modes and thus also tunes the device’s RI sensitivity. The tuning can be simply realized by varying number of cycles, which is proportional to thickness of the high-refractive-index (n<1.9 in infrared spectral range) ZnO film. The advantage of this approach is precision in determining the film thickness resulting in RI sensitivity of the LPGs.

Investigations of mutual thermal coupling between SiC Schottky diodes situated in the common case

Purpose This paper aims to present the results of measurements and calculations illustrating mutual thermal coupling between power Schottky diodes made of silicon carbide situated in the common case. Design/methodology/approach The idea of measurements of mutual transient thermal impedances of the investigated device is described. Findings The results of measurements of mutual transient thermal impedances between the considered diodes are shown. The experimentally verified results of calculations of the internal temperature waveforms of the considered diodes obtained with mutual thermal coupling taken into account are presented and discussed. The influence of mutual thermal coupling and a self-heating phenomenon on the internal temperature of the considered diodes is pointed out. Research limitations/implications The presented methods of measurements and calculations can be used for constructing the investigated diodes made of other semiconductor materials. Originality/value The presented results prove that mutual thermal coupling between diodes mounted in the common case must be taken into account to calculate correctly the waveforms of the device internal temperature.