Direct bandgap photoluminescence from n-type indirect GaInP alloys

Abstract

This work studies Te doping effects on the direct bandgap photoluminescence (PL) of indirect GaxIn1−xP alloys (0.72≤x≤0.74). The temperature-dependent PL shows that the energy difference between direct Γ valley and indirect X valleys is reduced due to the bandgap narrowing (BGN) effect, and the direct band transition gradually dominates the PL spectra as temperature increases. Carrier thermalization has been observed for Te-doped GaxIn1−xP samples, as integrated PL intensity increases with increasing temperature from 175 to 300 K. The activation energy for carrier thermalization is reduced as doping concentration increases. Both BGN effect and carrier thermalization contribute to the carrier injection into the Γ valley. As a result, the direct band transition is enhanced in the Te-doped indirect GaxIn1−xP alloys. Therefore, the PL intensity of the Ga0.74In0.26P sample with active doping concentration of 9×1017 cm−3 is increased by five times compared with that of a nominally undoped sample. It is also found that the PL intensity is degraded significantly when the doping concentration is increased to 5×1018 cm−3. From cross-section transmission electron microscopy, no large dopant clusters or other extended defects were found contributing to this degradation.