Effects of heat-treatments on electrical properties of boron-doped silicon crystals

The effects of heat-treatments around 1000°Ｃand subsequent annealing on the electrical properties of boron-doped silicon have been studied by electrical conductivity, Hall effect, and deep-level transient spectroscopy measurements. The high-temperature heat-treatments always induced net densities of donors. Four recovery stages, stages I-IV, of heat-treatment- induced donors were observed on isochronal annealing up to 400°Ｃ Conductivity changes in these stages can be explained as described below by the reactions of interstitial iron (Fei), its pair (Fe1Bs)with substitutional boron (Bs), and two unknown donors (D1, D2). That is, stage I (25°-100°Ｃ): D1→sink and Fei + Bs→FeiBs, stage II (100°-150°Ｃ)： FeiBs→Fei + Bs, stage III (200°-250°Ｃ):D2→sink, stage IV (250°-350°Ｃ)Fei→precipitation. Heat-treatments in an oxygen atmosphere greatly reduced the introduction of Fei and FeiBs in comparison with an argon atmosphere and mainly introduced D1 and D2 donors. The density of D2 was dependent on the heat-treatment temperature, while that of D1 showed almost no dependence. In stage I, D, was annihilated by first-order kinetics with an activation energy of 0.8 eV. It was indicated that DI and D2 have no relations to iron, copper, oxygen, nor carbon. Though their origins are still unidentified, there may be some interstitial impurities. In stage IV, Fei is suggested to precipitate at oxygen precipitates and dislocation loops formed by high-temperature heat-treatments. As to the application to iron gettering in the device fabrication process, it is proposed that annealing around 300°Ｃ is most suitable as the final heat-treatment step to remove iron and related defects from active regions of devices. Silicon wafers receive complex heat-treatments at various.</p

Development of the Coherent Differential Imaging on Speckle Area Nulling (CDI-SAN) Method

Various types of high-contrast imaging instruments have been proposed and developed for direct detection of exoplanets by suppressing nearby stellar light. Stellar speckles due to wavefront aberration can be suppressed by the appropriate wavefront control, called the dark hole control. However, the speckles, which fluctuate faster than the dark hole control due to atmospheric turbulence in ground-based telescopes or instrument deformation caused by temperature changes in space telescopes, cannot be suppressed by the control and remain in focal plane images. The Coherent Differential Imaging on Speckle Area Nulling (CDI-SAN) method was proposed to overcome such fast fluctuating speckles and detect exoplanetary light. We constructed an optical setup in a laboratory to demonstrate the CDI-SAN method. With the dark hole control and the CDI-SAN method, we achieved 10−8 level of contrasts. © 2023 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]