Photoluminescence of phosphorus atomic layer doped Ge grown on Si

Improvement of the photoluminescence (PL) of Phosphorus (P) doped Ge by P atomic layer doping (ALD) is investigated. Fifty P delta layers of 8 x 10(13) cm(-2) separated by 4 nm Ge spacer are selectively deposited at 300 degrees C on a 700 nm thick P-doped Ge buffer layer of 1.4. x 10(19) cm(-3) on SiO2 structured Si (100) substrate. A high P concentration region of 1.6 x 10(20) cm(-3) with abrupt P delta profiles is formed by the P-ALD process. Compared to the P-doped Ge buffer layer, a reduced PL intensity is observed, which might be caused by a higher density of point defects in the P delta doped Ge layer. The peak position is shifted by similar to 0.1 eV towards lower energy, indicating an increased active carrier concentration in the P-delta doped Ge layer. By introducing annealing at 400 degrees C to 500 degrees C after each Ge spacer deposition, P desorption and diffusion is observed resulting in relatively uniform P profiles of similar to 2 x 10(19) cm(-3). Increased PL intensity and red shift of the PL peak are observed due to improved crystallinity and higher active P concentration.