Position sensitive detectors (PSDs) comprise optical sensors used in applications such as robotic vision, machine tool
alignment and other precision measurements. This paper will report on a series of Schottky Barrier crystalline silicon
devices which display marked advantages including rapid response times, easier fabrication techniques and high
sensitivities compared with most other research work now being concentrated on PECVD amorphous silicon structures.
In this work, results from devices fabricated from substrates with a range of resistivities and various Schottky metals are
presented. Some of the sensitivity measurements obtained are better than 25 mV/mm which are some of the best
sensitivities reported for Schottky barrier crystalline PSDs. These results were obtained coincidentally with excellent
linearities. Devices were also tested under a range of light beams including very low broadband white light levels of
0.1mW up to 10mW. The highest and most linear outputs occurred under different conditions for each substrate
resistivity and Schottky metal. Also observed were the different effects that background illumination had on each set of
devices, the biggest effect being on the highest resistivity devices.
Thin film optical position sensitive detectors (PSDs) based on novel hydrogenated amorphous silicon Schottky barrier (SB) structures are compared in this work. The three structures reported here have been tested under different light sources to measure their linear properties and wavelength response characteristics. The sputtered a-Si sensors were configured as layered structures of platinum, a-Si and indium tin oxide, forming SB-i-n devices and exhibited linear properties similar to multi-layer a-Si p-i- n devices produced by complex chemical vapor deposition procedures, which involve flammable and toxic gases. All structures were test4ed as possible configurations for 2D sensors. The devices were tested under white light, filtered white light and also a red diode laser. Each of the three structures responded quite differently to each of the sources. Results, based on the correlation coefficient, which measures the linearity of output and which has a maximum value of 1, produced r values ranging between 0.992 to 0.999, in the best performances.
With an energy gap of 1.34 eV, indium phosphide (InP) is an ideal material for solar energy conversion. Much work has been carried out on sputtered indium-tin-oxide (ITO)/InP solar cells but modeling of this structure has long been the subject of debate. The double-layer structure used in this work was originally devised to minimize the surface degradation of InP when exposed to normal heating steps during the fabrication process due to the low congruent temperature of InP. We deposited a thin protective layer of either ITO or indium-tin to protect the front surface of the InP before any heating stages took place. A second layer, ITO, was then deposited to compete the junction. Variation of film deposition conditions, thicknesses and annealing steps worked to improve device performances as well as provide insight into junction mechanisms.
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