The report summarizes work done in two areas during the period September 1, 1973 through February 28, 1974. The first of these is a continuation of work on aluminum-alloyed silicon grating cells. Work on optimization of the geometryn(grating line width and spacing) confirms the previously presented analysis of such cells. A 1 cm2 grating cell has been fabricated and its i-V characteristicnhas been measured under an AMO solar simulator;it is found that the efficiency of this cell would be about 7.9% if it were covered by the usual anti-reflectionncoating. Note that the surface of the cell is not covered by a diffused junction.nThe response is blue shifted;the current is somewhat higher than that produced by a commercial Si cell. However the open circuit voltage is low and attempts to optimize the open circuit voltage of the aluminum-alloy junctions are described.nThe second area of investigation is a preliminary X-ray topographic examination of GaAs specimens of the type commonly used to make solar cells. The X-ray study shows that the wafers are "filled" with regions having strain gradients, possibly caused by precipitates. It is possible that a correlation exists between the presence of low mechanical perfection and minority carrier diffusion lengths of GaAs crystals.
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