Wavelength-tunable infrared light emitting diode based on ordered ZnO nanowire/Si_1–xGe_x alloy heterojunction

A novel infrared light emitting diode (LED) based on an ordered p-n heterojunction built of a p-Si_1–xGe_x alloy and n-ZnO nanowires has been developed. The electroluminescence (EL) emission of this LED is in the infrared range, which is dominated by the band gap of Si_1–xGe_x alloy. The EL wavelength variation of the LED shows a red shift, which increases with increasing mole fraction of Ge. With Ge mole fractions of 0.18, 0.23 and 0.29, the average EL wavelengths are around 1, 144, 1, 162 and 1, 185 nm, respectively. The observed magnitudes of the red shifts are consistent with theoretical calculations. Therefore, by modulating the mole fraction of Ge in the Si_1–xGe_x alloy, we can adjust the band gap of the SiGe film and tune the emission wavelength of the fabricated LED. Such an IR LED device may have great potential applications in optical communication, environmental monitoring and biological and medical analyses.