Considering tensile-strained p-type Si/Si 1−y Ge y quantum wells grown on a relaxed Si 1−x Ge x (0 0 1) virtual substrate (y < x), the hole subband structure and the effective masses of the first bound hole state in the quantum wells are calculated by using the 6 × 6 k • p method. Designs for tensile-strained p-type quantum well infrared photodetectors (QWIPs) based on the bound-to-quasi-bound transitions are discussed, which are expected to retain the ability of coupling normally incident infrared radiation without any grating couplers, have lower dark current than n-type QWIPs and also have a larger absorption coefficient and better transport characteristics than normal unstrained or compressive-strained p-type QWIPs.

We have investigated the growth of thin selenium layer on Si (100) substrate by molecular beam epitaxy (MBE). By controlling the temperatures of the silicon substrate and the selenium source during growth, an ultrathin film of Se is successfully grown on the Si (100) substrate. As the Si (100) surface is passivated by the ultrathin film of Se, the electrical property of the Ti/n-Si (100) contact is shown to be ideally ohmic, with low resistance and relatively high thermal stability.

We have investigated the structure and photoluminescence (PL) properties of Se nanocrystals (NCs) obtained by rapid thermal annealing of a-Se films on Si substrate. The size of Se NCs in a trigonal phase increases linearly with increasing temperature. Moreover, three PL peaks located at 1.4, 1.7 and 1.83 eV are observed, which are attributed to the emission of defects in amorphous Se, donor-acceprter pair (DAP) recombination at the interface of amorphous Se and Se NCs, and interband transition of Se crystals, respectively.