Temperature (T)-dependent photoluminescence (PL) has been investigated for both p-Ge and n-Ge1-ySny films grown on Si substrates. For the p-Ge, strong direct bandgap (ED) along with weak indirect bandgap related (EID) PL at low temperatures (LTs) and strong ED PL at room temperature (RT) were observed. In contrast, for the n-Ge1-ySny, very strong dominant EID PL at LT and strong ED PL were observed at RT. This T-dependent PL study indicates that the indirect-to-direct bandgap transitions of Ge1-ySny might take place at much lower Sn contents than the theory predicts, suggesting that these Ge1-ySny could become very promising direct bandgap semiconductors.

Previously developed methods used to grow Ge1−ySny alloys on Si are extended to Sn concentrations in the 1019−1020 cm−3 range. These concentrations are shown to be sufficient to engineer large increases in the responsivity of detectors operating at 1550 nm. The dopant levels of Sn are incorporated at temperatures in the 370–390 °C range, yielding atomically smooth layers devoid of threading defects at high growth rates of 15–30 nm/min. These conditions are far more compatible with complementary metal-oxide semiconductor processing than the high growth and processing temperatures required to achieve the same responsivity via tensile strain in pure Ge on Si. A detailed study of a detector based on a Sn-doped Ge layer with 0.25% (1.1 × 1020 cm−3) Sn range demonstrates the responsivity enhancement and shows much better I-V characteristics than previously fabricated detectors based on Ge1−ySny alloys with y = 0.02.

A photovoltaic device was successfully grown solely based on the single ZnO p-n homojunction nanowire. The ZnO nanowire p-n diode consists of an as-grown n-type segment and an in situ arsenic-doped p-type segment. This p-n homojunction acts as a good photovoltaic cell, producing a photocurrent almost 45 times larger than the dark current under reverse-biased conditions. Our results demonstrate that the present ZnO p-n homojunction nanowire can be used as a self-powered ultraviolet photodetector as well as a photovoltaic cell, which can also be used as an ultralow electrical power source for nanoscale electronic, optoelectronic and medical devices.

Fe ions of dose 5×1016cm−2 were implanted at 200keV into a-plane ZnO epitaxial films. The epitaxial quality of the postannealed samples was verified by x-ray diffraction ω-rocking curves and φ scans, whereas x-ray absorption spectroscopy identified the presence of both Fe2+ and Fe3+ ions, as well as changes in their relative concentration during postannealing. Superconducting quantum interference device measurements show that the as-implanted and postannealed films are ferromagnetic at room temperature. The saturation magnetization reduces during annealing possibly due to the decrease in the number of oxygen vacancies.

Electrical activation studies of Si-implanted GaN grown on sapphire have been made as a function of ion dose and anneal temperature. Silicon was implanted at 200 keV with doses ranging from 1×1013 to 5×1015 cm−2 at room temperature. The samples were annealed from 1100 to 1350 °C with a 500-Å-thick AlN cap in a nitrogen environment. Samples implanted with high doses (⩾1×1015 cm−2) have optimum anneal temperatures of around 1350 °C, exhibiting a nearly 100% electrical activation efficiency, whereas low dose (⩽5×1014 cm−2) samples exhibited lower activation efficiencies, but efficiencies increase with anneal temperature even after annealing at 1350 °C.