Photoconductive gain of SiGe/Si quantum well photodetectors

A SiGe/Si Multiple Quantum Wells (MQWs) structure is proposed for highly sensitive photodetection. A large photoconductive gain is obtained because of the unique SiGe/Si band structure, i.e., a large band offset in the valence band, but a small band offset in the conduction band. Such a structure allows the trapping of photogenerated holes inside the valance band quantum wells. Alternatively, photogenerated electrons appear in shallow quantum wells and have relatively high mobility. These give rise to a large photoconductive gain. The calculated photoconductive gain for this structure exceeds 2 × 107. Experimental results confirmed a high gain of the structure.