Space-charge spectroscopy of self-assembled Ge-rich dots on Si grown by MBE

The results of deep-level transient spectroscopy and admittance measurement s of self-assembled Ge-rich dots are presented. The investigated quantum we ll (QW) Ge-rich layers in silicon consist of a thin-wetting QW layer with a width of 4-4.5 monolayers and three-dimensional dots (islands), with heigh ts of about 6-8.5 Nm and lateral dimensions of about 190-250 nm. Good agree ment was observed with photoluminescence data. An enhancement of the latera l hole transport between the islands via the wetting layer due to thermally activated tunneling was observed. This effect is explained by a strong lat eral electric field, which is induced by Coulomb charge of confined holes i n the disc-shaped islands. [S0163-1829(99)03516-X].