High-voltage micro solar cell arrays of GaAs with output voltage up to 100 V

Arrays of micro-solar cells connected in series were fabricated on GaAs wafers of millimeter sizes. Arrays of 24 and 120 cells generated open-circuit voltages of 20 and 100 V, respectively, under illumination with the optical power density of 100 mW/cm/sup 2/. Each micro cell has a photo-sensitive area of 120 /spl mu/m/spl times/70 /spl mu/m, and the short-circuit current are in the /spl mu/A range. Gallium arsenide was selected because of its availability of semi-insulating substrates and various epilayers including mixed crystals. Leakage current in the substrate under illumination was prevented by forming a shielding film of gold on the surface except the receiving areas of the solar cells. Responses to transient light were examined from the viewpoint of applications. To obtain high output voltage, high load resistance on the order of 10 M/spl Omega/ is required, which limits the response time to 10 ms. The high-voltage output will be of great use for miniaturized electrostatic or piezoelectric actuators.