Germanium Wafers: June 2018

Jun 25, 2018

Defect complexes in fluorine-implanted germanium

In the present article we employ positron annihilation lifetime spectroscopy and secondary ion mass spectrometry to study the thermal evolution of vacancy related defects in fluorine-implanted germanium. We find that fluorine enriches the germanium matrix with various vacancy-like clusters that show both concentration and annealing temperature-dependent behaviour. We demonstrate that low fluorine concentrations saturate the Ge matrix with large concentrations of divacancy-like complexes that are effectively removed after moderate annealing. High fluorine concentrations, however, appear to stabilize a large component of monovacancy-like complexes in the near-surface region of the Ge substrates. These monovacancy-like complexes also appear to be thermodynamically stable, even after high-temperature annealing. The nucleation and thermal evolution of these vacancy-like defects may have particular importance in the fabrication and control of future germanium electronic devices.

Source:IOPscience

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Jun 4, 2018

Ultralarge transient optical gain from tensile-strained, n-doped germanium on silicon by spin-on dopant diffusion

The direct band gap optical gain of tensile-strained, highly n-doped germanium on silicon is investigated by femtosecond ultrafast transmittance spectroscopy. A germanium film with 0.22% tensile strain is grown on a silicon substrate by using molecular beam epitaxy. An activated doping concentration up to 4 × 1019 cm−3 is achieved by phosphorus diffusion from a spin-on dopant source. The transmittance of the germanium film is clearly increased upon increasing the pump power. A peak optical gain of up to 5300 cm−1 around 1.7 µm and a gain spectrum broader than 300 nm are obtained. These results show a simple yet promising way to realize gain medium for monolithic-integrated germanium lasers.