ULTRAFAST ELECTRON AND HOLE TUNNELING IN (GA,IN)AS (AL,IN)AS ASYMMETRIC DOUBLE-QUANTUM WELLS/

We present unambiguous experimental evidence for the dramatic dependen ce of hole tunneling rates on in-plane momentum in (Ga,In)As/(Al,In)As asymmetric double quantum wells. Holes generated near the band edge t unnel on hundred picosecond time scales, whereas holes excited with la rge excess energy tunnel on subpicosecond time scales. The mechanism r esponsible for this increase of more than three orders of magnitude in the hole tunneling rate is nonresonant delocalization of hole wave fu nctions by band mixing in the valence band. (C) 1996 American Institut e of Physics.