Open AccessStudy on epsilon crossover wavelength tuning of heavily doped germanium-on-silicon in mid-infrared range
Author(s) -
Zhewei Wang,
Haining Chong,
Jianhan Yang,
Hui Ye
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.033724
Subject(s) - germanium , materials science , doping , optoelectronics , silicon , dopant , molecular beam epitaxy , substrate (aquarium) , infrared , semiconductor , optics , epitaxy , nanotechnology , physics , oceanography , layer (electronics) , geology
In this paper, we demonstrate that n-type heavily doped germanium (Ge) can serve as a sort of CMOS-compatible, permittivity crossover wavelength (at which the real part of permittivity changes sign) wide range adjustable epsilon-zero material in mid-infrared (MIR). The antimony (Sb) doped Ge films with high doping concentrations have been highly crystalline grown on silicon substrates with the molecular beam epitaxy (MBE) process. Our results reveal that the crossover wavelength of doped germanium is highly tunable by adjusting the carrier concentration and crystallinity of the films simultaneously. By optimizing dopant flux and substrate temperature, the maximum carrier concentration can be achieved as high as 1.6×10 20 cm -3 , resulting in a very short crossover wavelength of 4.31 µm, which is very difficult to realize in group IV semiconductors. The heavily doping process also enables it possible to observe the room temperature photoluminescence (PL) from direct band transition of germanium films.