By combining a bottom-up, i.e., thermal evaporation method, and the top-down technologies, i.e., molecular beam epitaxy, the spherical SiGe quantum dot infrared photodetectors (QDIP) have been successfully fabricated for the first time. The thermal evaporation method was chosen to synthesize spherical SiGe nanoparticles. They are treated with methanol containing alumina powders in the ultrasonic bath to form a single SiGe dot layer with density about 1.6 X 10(11) cm(-2). The QDIP exhibits two response regions, i.e., 1-3.5 and 14-20 mum. The peak responsivity of QDIP is 5.4 mA/W at 2 mum and about 0.6 mA/W at 17 mum at a bias of 200 mV. This QDIP also exhibits photovoltaic response, a short circuit current exists at zero bias. This device is capable of operating up to 240 K with good performance. (C) 2004 American Vacuum Society.