Making germanium, an indirect band gap semiconductor, suitable for light-emitting devices *Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam. (6th January 2015)

• Record Type: Journal Article
• Authors: Luong, Thi Kim Phuong; Thanh, Vinh Le; Ghrib, Abdelhamid; Kurdi, Moustafa El; Boucaud, Philippe
• Is Part Of: Advances in natural sciences. Volume 6:Number 1(2015)
• Publication Date: 2015-01-06
• Subjects: tensile strain -- heavy n-doping -- Ge band gap engineering -- GaP decomposition -- group-IV semiconductor; 4.10 -- 5.03 -- 5.04; Nanotechnology -- Periodicals; Nanoscience -- Periodicals; 620.5
• DOI: 10.1088/2043-6262/6/1/015013
• Languages: English
• ISSNs: 2043-6254

Abstract

Abstract: Germanium (Ge) is a group-IV indirect band gap semiconductor but the difference between its direct and indirect band gap is only 140 meV. It has been shown that when Ge is subjected to a tensile strain and a heavy n -doping level, room-temperature photoluminescence (PL) can be greatly enhanced. Among these two factors, achieving a heavy n -doping level in Ge (i.e., electron concentrations higher than 1 × 10 19 cm −3 ) is a challenge since the solubility of most group-V elements (P, As, Sb) in Ge is very low. We report here Ge growth on silicon substrates using molecular beam epitaxial (MBE) technique. To enhance the n -doping level in Ge, a specific n -doping process based on the decomposition of the GaP compound has been implemented. The GaP decomposition allows producing P2 molecules, which have a higher sticking coefficient than that of P4 molecules. We show that phosphorus doping at low substrate temperatures followed by flash thermal annealing are essential to get a high doping level. We have obtained an activate phosphorus concentration up to 2 × 10 19 cm −3 and room-temperature PL measurements reveal an intensity enhancement up to 50 times. This result opens a new route for the realization of group-IV semiconductor optoelectronic devices.