Silicon, the leading material in microelectronics during the last four
decades, also promises to be the key material in the future. Despite
many claims that silicon technology has reached fundamental limits, the
performance of silicon microelectronics continues to improve steadily.
The same holds for almost all the applications for which Si was
considered to be unsuitable. The main exception to this positive trend
is the silicon laser, which has not been demonstrated to date. The main
reason for this comes from a fundamental limitation related to the
indirect nature of the Si band-gap. In the recent past, many different
approaches have been taken to achieve this goal: dislocated silicon,
extremely pure silicon, silicon nanocrystals, porous silicon, Er doped
Si-Ge, SiGe alloys and multiquantum wells, SiGe quantum dots, SiGe
quantum cascade structures, shallow impurity centers in silicon and Er
doped silicon. All of these are abundantly illustrated in the present
book.