Mittuniversitetet

Position sensingdetectors (PSDs) are useful in many applications, such as vibration, displacement, and triangulation measurements. In this paper we present a lateral-effect metal oxide semiconductor PSD with switchingcapability fabricated by our group. The detector can be switched off by the application of 0V on the substrate and 0.2V on the gate. A linear current-position behaviour is exhibited by the detector at a substrate bias of both 5 and 10V with the gate at 0V. There is no effect on the linearity when the substrate voltage is changed from 5 to 10V. The non-linearity is within 0.2% at a distance of 71.5mm from origin for 5, 10 and 15mm device length.

Position-sensitive detectors (PSDs) are widely used in noncontact measurement systems. In order to minimize the size of such systems, interest has increased in mounting the PSD chip directly onto printed circuit boards (PCBs). Stress may be induced in the PSD because of the large differences in thermal expansion coefficients, as well as the long-term geometrical stability of the chip packaging. Mechanical stress has previously been shown to have an effect on the performance of semiconductors. The accuracy, or linearity, of a lateral effect PSD is largely dependent on the homogeneity of the resistive layer. Variations of the resistivity over the active area of the PSD will result in an uneven distribution of photo-generated current, and hence an error in the readout position. In this work experiments were performed to investigate the influence of anisotropic mechanical stress in terms of nonlinearity. PSD chips of 60×3 mm active area were subjected, respectively, to different amounts of compressive and tensile stress to determine the influence on the linearity.

The characterization and design of a Fourier transform spectrometer, which enables the integration of a multi channel interferometer with a detector unit in order to create a compact device is presented in this paper. It operates within a wide spectral range from visible to NIR, contains no moving parts and is resistible to mechanical and climatic conditions. Such a design with an array or matrix detector can be used for spectroscopy with a partially coherent or white optical source depending on the shape of the optical interferometer. A reasonable spectral resolution of the order of 20-50 cm-1 can be achieved over a 1 µm wavelength range when using a 512 pixel detector array. A design model for characterization of the quasi integrated device, where a multi channel interferometer was mechanically attached and which contained a gap to the detector elements, was used. The experimental results are promising and suggest a variety of different directions for the development and application of these types of integrated spectrometers.

Porous Silicon (PS) has attracted much attention since the discovery of its photo luminescent behavior. It has also been used for various other applications such as electroluminescent light emitting-diodes (LEDs), photodetectors and solar cells. For such devices, it is important to make good metallic Ohmic contacts to the PS in order to maximize the efficiency. In order to produce buried contacts, barrier layers, Schottky devices, etc. in PS, it is advantageous to deposit metal that covers not only the surface of the porous layer, but also the inside walls and the bottom of the pores. In this work experiments were performed to examine the morphology and properties of electroless deposition of Nickel into p-type PS and subsequent formation of Nickel silicide after heat treatment. Circular PS samples of 6 mm diameter were produced by anodizing p-type Silicon wafers for 15 min and were subsequently plated with Ni using three different plating baths. The pores are on average 20 µm deep and 4 µm wide. Two samples of each type were heat treated in an nitrogen atmosphere for one hour at 400 and 600°C respectively to produce Nickel silicide. Reference samples were made by means of electron beam evaporation of Ni. SEM micrographs show that the best pore coverage was achieved using the Ni plating bath containing hypophosphite. I–V characterization shows that different rectifying and Ohmic contacts can be formed between electroless deposited Ni and PS depending on the conditions of the heat treatment. XRD and EDX characterizations show that both the NiSi and Ni₂Si phases exist in the sample at the same time.