Wavelength-tunable infrared light emitting diode based on ordered ZnO nanowire/Si1-xGex alloy heterojunction

A novel infrared light emitting diode （LED） based on an ordered p-n heterojunction built of a p-Si1-xGe/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 Si1-xGex 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 Si1-xGex 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.