LUMINESCENCE OF STRAINED SI1-XGEX/SI QUANTUM-WELLS AND MICROSTRUCTURES

We present a study on luminescence of strained Si1-xGex/Si heterostructures, highlighting features characteristic of ''indirect gap'' strained Si1-xGex/Si quantum wells (QWs). It is shown that the QW alone cannot be viewed as an independent system isolated from Si barriers. Rather, the important role of Si barrier layers is addressed on the basis of luminescence decay lifetime measurements and steady-state luminescence observations. Conversely, the QW should not stand as a strictly two-dimensional system and a volume effect is playing a major role in the interpretation of optical properties of the QWs when the excitation light is in the energy range above the Si barrier band gap. This is in marked contrast to the direct gap materials system and reflects the intrinsic aspect of the ''indirect gap'' nature of the SiGe QW systems. The Si layer quality was further assessed in terms of spectral intensity of double QW systems by systematically changing the cap Si layer thickness, It will be finally shown that an appropriate sample metry taking account of carrier generation and transport leads to the development of quantum confined photoluminescence at room temperature.