Gate controlled Ge/SiGe QD/QW photo-MESFETs for high photo-response at 1.31-1.55 μm

This paper demonstrates the fabrication of near infrared MESFET photodetectors. This study shows that photon absorption occurs in Ge quantum dots while the lateral transport of photo-carriers is facilitated by high mobility 2D SiGe quantum wells next to the dot layers. High photo-response at normal incidence are measured, with the highest responsivity of 140 mA/W (1.31 /spl mu/m) and >35 mA/W (1.55 /spl mu/m) at room temperature. The measured integrated photo-responsivity for the photon beam with energies below the Si bandgap is >200 mA/W at V/sub DS/ = -2.5 V and V/sub G/ = 2 V. The time-resolved photoconductivity measurements and switch properties of these MESFET photodetectors are also studied with switching frequency of 3 MHz, which is the upper limit of the instrument bandwidth.