We have studied the impact of temperature and pressure on the structural and electronic properties of Ge:P layers grown with GeH4+PH3 on thick Ge buffers, themselves on Si(0 0 1). The maximum phosphorous atomic concentration [P] exponentially decreased as the growth temperature increased, irrespective of pressure (20 Torr, 100 Torr or 250 Torr). The highest values were however achieved at 100 Torr (3.6 x 10(20) cm(-3) at 400 degrees C, 2.5 x 10(19) cm(-3) at 600 degrees C and 10(19) cm(-3) at 750 degrees C). P atomic depth profiles, "box-like" at 400 degrees C, became trapezoidal at 600 degrees C and 750 degrees C, most likely because of surface segregation. The increase at 100 Torr of [P] with the PH3 mass-flow, almost linear at 400 degrees C, saturated quite rapidly at much lower values at 600 degrees C and 750 degrees C. Adding PH3 had however almost no impact on the Ge growth rate (be it at 400 degrees C or 750 degrees C). A growth temperature of 400 degrees C yielded Ge:P layers tensily-strained on the Ge buffers underneath, with a very high concentration of substitutional P atoms (5.4 x 10(20) cm(-3)). Such layers were however rough and of rather low crystalline quality in X-ray Diffraction. Ge:P layers grown at 600 degrees C and 750 degrees C had the same lattice parameter and smooth surface morphology as the Ge:B buffers underneath, most likely because of lower P atomic concentrations (2.5 x 10(19) cm(-3) and 10(19) cm(-3), respectively). Four point probe measurements showed that almost all P atoms were electrically active at 600 degrees C and 750 degrees C (1/4th at 400 degrees C). Finally, room temperature photoluminescence measurements confirmed that high temperature Ge:P layers were of high optical quality, with a direct bandgap peak either slightly less intense (750 degrees C) or more intense (600 degrees C) than similar thickness intrinsic Ge layers. In contrast, highly phosphorous-doped Ge layers grown at 400 degrees C were of poor optical quality, in line with structural and electrical results. (C) 2012 Elsevier B.V. All rights reserved.