  With the aim of improving solar cell efficiency, a structure for realizing
electron tunneling from In0.6Al0.4As quantum dots (QDs) through an Al0.4Ga0.6As
barrier to AlAs has been grown using molecular beam epitaxy. The
photoluminescence decay time decreased from 1.1 ns to 390 ps as the barrier
thickness decreased from 4 to 2 nm, which indicates that the photo-excited
carriers tunneled from the QDs to the AlAs X energy level for a barrier
thickness 2 nm in 0.6 ns, which is significantly longer than the tunneling time
of GaAs and InAlAs quantum wells. We expect that this structure will assist in
developing high-efficiency QD sensitized solar cells.
