A new effect is being developed which significantly improves the conversion efficiency of antireflection-coated metal-oxide-semiconductor ‘AMOS’ solar cells. The effect, a marked increase in the open-circuit voltage, is produced by the addition of an oxide layer to the semiconductor. Cells using gold on n-type gallium arsenide have been made with efficiencies up to 15% in terrestrial sunlight. All processing steps are amenable to the use of low-cost polycrystalline films of GaAs in place of the single crystals now used.
Galvanomagnetic measurements have been carried out on a number of single-crystal samples of w-AlSb(Te), with room-temperature carrier concentrations between 5X10 16 cm -3 and 2.5XlO 17 cm" 3 . The measurements were carried out over the temperature range 77 to 500°K. An impurity activation energy, extrapolated to 0°K, of 0.068 eV is obtained from the Hall data. Above 250°K, the temperature dependence of the Hall mobility is proportional to J 1-1 -8 . Magnetoresistance measurements were performed at fixed temperatures in the range 77 to 295 °K. The magnetoresistance was found to be proportional to H 2 up to at least 30 kG. The relations between the various magnetoresistance coefficients follow very closely those required for a [100] multivalley conduction band. The anisotropy parameter K -(mu/mi)(ri/ri\) is found to be ^7 at room temperature in the sample of lowest carrier concentration (where the m's are the effective masses and the r's the relaxation times referred to directions parallel and perpendicular to the unique axis of a spheroidal surface of constant energy). This value decreases to ^3 at 77°K, suggesting increasing anisotropy of scattering due to ionized impurities. An argument is presented in favor of the prolateness of the ellipsoids. Assuming TU/TI=1, K-7, six valleys, and a conductivity effective mass of O.SOmo (where mo is the freeelectron mass), we obtain wn = 1.50mo, mi-0.21mo, and a density-of-states mass mz>* = 1.34mo.
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