Photo- and electroluminescence characterization of erbium doped SiGe

Abstract

We have performed photo-and electroluminescence measurements on erbium doped silicon and SiGe samples containing different amounts of germanium. All samples were grown completely by molecular beam epitaxy. Oxygen was used as a codopant to enhance the luminescence efficiency. The photoluminescence data show a systematic variation of the thermal activation energy obtained from temperature dependent intensity measurements with varying germanium contents. For samples with an alternating Si/SiGe layer structure stronger photoluminescence is observed when the erbium ions are incorporated into the SiGe layers rather than into the silicon layers. We attribute this to the capture of photogenerated carriers in the SiGe layers. Electroluminescence from erbium doped SiGe samples which have been processed as diodes has been observed up to room temperature in both surface and edge emitting geometries.

Erbium-doped Si1-xGex/Si structures for light emitting diodes

“…The quenching energies and coupling coefficients are very similar, especially for the higher temperature process. It can be seen from table 2 that not only do the activation energies of the highest temperature processes decrease with increasing Ge, as reported before [5], but the coupling coefficients increase with increasing Ge concentration. It is difficult to deduce much from the value of the coupling coefficient, especially as widely differing values have been observed for different erbium sitings [26].…”

“…The intensities of the Er emission from the samples are very similar, although this was only achieved by co-implanting O into sample 5 in addition to the Er. This leads to the suggestion that the excitation and/or energy transfer process is more efficient when the Er is in an Si/SiGe quantum well system, a view also expressed in the literature [4,5,7].…”

“…High concentrations of erbium are required in the silicon, and this can only be achieved by non-equilibrium methods. Hence the vast majority of the reported work in the literature is on erbium doping by implantation, or erbium doping during MBE growth [4,5]. The implantation route has the added advantage of being compatible with established silicon processing techniques.…”

“…The majority of the literature on erbium-doped siliconbased electroluminescent devices has been on diodes that operate in reverse bias [4][5][6][7][8][9] because it has been widely reported that the electroluminescence at 1.54 µm persists up to room temperature in this mode of operation. This is Corresponding author.…”

“…An optoelectronic device, such as a laser, requires a structure that will provide waveguiding. There has recently been considerable interest in the use of Si 1−x Ge x embedded in silicon as a waveguide [4,5,[10][11][12][13][14]. The refractive index of an SiGe alloy is determined by the Ge concentration [10] and any strain present also modifies the refractive index.…”