Photocurrent and transmission spectroscopy of direct-gap interband transitions in Ge∕SiGe quantum wells

The authors studied the direct-gap interband transitions in strain-compensated Ge∕SiGe quantum wells grown by low energy plasma enhanced chemical vapor deposition. A series of excitonic interband absorptions from the quantized hole states to the quantized electronic states at the Γ7c− edge in the Ge wells is observed up to room temperature by photocurrent and transmission spectroscopy. The results are compared with theory. At low temperature, the quantum confined Stark effect is demonstrated in a Schottky diode geometry.