Enhanced active P doping by using high order Ge precursors leading to intense photoluminescence

•Very low temperature in-situ P doping to Ge using Ge2H6 and PH3•Achievement of the highest active P concentration among the reported values•Study of the impact of growth temperature and activation of P on PL intensity

The impact of the growth temperature on the in-situ phosphorus doped Ge layer grown by chemical vapor deposition is studied to achieve a sufficiently high n-type carrier concentration for the realization of the quasi-direct band gap material in Ge. The use of a high order precursor gas, namely Ge2H6, allows to reduce the growth temperature down to 320 °C without degrading the material quality in view of optical applications. An active phosphorus concentration as high as 6.2 × 1019/cm3 has been measured by Hall effect measurements. The achieved active phosphorus concentration is the highest among the reported concentrations for uniformly in-situ doped Ge layers. The high and almost fully (87%) activated phosphorus concentration results in a strong photoluminescence peak at room temperature, which intensity is 8.3 times higher compared to the photoluminescence intensity as measured for an undoped Ge layer.