Molecular beam epitaxy grown GaInP top cells and GaAs tunnel diodes for tandem applications

Ga/sub 0.51/In/sub 0.49/P solar cells and GaAs tunnel diodes were grown by gas-source molecular beam epitaxy. The effect of various window layer materials, such as Al/sub 0.51/In/sub 0.49/P, Al/sub 0.8/Ga/sub 0.2/As and ZnSe were studied for n-on-p Ga/sub 0.51/In/sub 0.49/P cells. The best carrier collection was obtained with Al/sub 0.51/In/sub 0.49/P window and with graded doping in emitter and base layers. A total-area AM0 efficiency of 14.0% for 2/spl times/2 cm/sup 2/ area has been measured for this cell. The GaAs tunnel diodes were grown with Be-doping for p-type and Si-doping for n-type material. Specific resistance of 0.09 m/spl Omega/cm/sup 2/ and peak tunneling current of 200 A/cm/sup 2/ were obtained for the best GaAs tunnel diodes. In addition, tunneling effect in a n++Ga/sub 0.51/In/sub 0.49/P/p++GaAs diode was observed.