Room temperature photoluminescence of bulk and doped Ge using an additional excitation source.*

Over the past 50 years, silicon (Si) has been fundamental in the electronics industry. The stable oxide, silicon dioxide (SiO₂) as well as the abundance of Si, has allowed for the growth of a multi-billion-dollar industry. If a proper light source could be achieved on Si it would revolutionize the photonics industry. Signal processing speed could be increased by orders of magnitude resulting in greater bandwidth in signal transmission. However, the limitations of Si prevent it from being used as an efficient light source.  Germanium (Ge) can be used to create an on Si light source. Furthermore, it has been shown that doping can enhance the direct emission of Ge. In 2012, an electrically-pumped Ge diode laser was demonstrated but its efficiency was low. Understanding the luminescence properties of Ge while under high-injection conditions produced through external excitation could lead to new device designs and improvements in efficiency. In this research, we performed pump-probe experiments on bulk intrinsic and doped Ge using a 1550 nm CW external pump at a wide range of intensities combined with a 980 nm modulated probe at low intensity and measured the resulting luminescence spectrum. It was observed that direct band luminescence was enhanced with increasing pump intensity.