Study of Self-assembled Ge Quantum Dot Infrared Photodetectors

Si based Ge quantum dot infrared photodetector (QDIP) has the potential of being a serious candidate for applications in optical fiber communications. In this paper, 20 periods of stacked Ge quantum dots were grown on Si(100) by gas source molecular beam epitaxy (GSMBE). Using the stacked quantum dots as active region, a P-I-N structure quantum dot infrared photodetector was fabricated. To improve absorptivity, then responsivity of QDIP, transfer matrix method was used to calculate the absorptivity (at 1.31 mum) for different thickness of Si spacer layers and different periods of Ge/Si bilayers. The simulation results showed that 20 periods of Ge/Si bilayers and 25 nm of Si spacer layers provided higher absorptivity. At room temperature, I-V measurement showed a low dark current density of 1.1 times 10^-5 A/cm² with applied voltage of -1V. A photocurrent responsivity of 0.158 mA/W was achieved at 1.31 mum. Compared with results we fabricated before [Wei et al., 2005], the responsivity was improved. The experimental results agree well with the simulation results