Enhancement of the hole photocurrent in layers of Ge/Si quantum dots with abrupt heterointerfaces

The photoconductive gain, hole photocurrent spectra in the mid-infrared range, and band-to-band photoluminescence spectra in arrays of Ge/Si quantum dots with different elemental compositions of the heterointerface are measured. The diffusive mixing of the materials of the matrix and the dots is controlled by varying the temperature at which the Ge layers are overgrown with Si. It is found that the formation of abrupt heterointerfaces leads to the enhancement of the hole photocurrent and quenching of photoluminescence. The results are explained by an increase in the lifetime of nonequilibrium holes owing to the suppression of their capture into the bound states of quantum dots.