Massachusetts Institute of Technology

Yan Cai

Lionel Cooper Kimerling

Jurgen Michel

Jifeng Liu

Jonathan T Bessette

Rodolfo E Camacho-Aguilera

Anuradha Murthy Agarwal

Pao Tai Lin

In a method for electrically doping a semiconducting material, a layer of germanium is formed having a germanium layer thickness, while in situ incorporating phosphorus dopant atoms at a concentration of at least about 5&#xd7;10cmthrough the thickness of the germanium layer during formation of the germanium layer. Additional phosphorus dopant atoms are ex situ incorporated through the thickness of the germanium layer, after formation of the germanium layer, to produce through the germanium layer thickness a total phosphorus dopant concentration of at least about 2&#xd7;10cm.

Method for high-concentration doping of germanium with phosphorous

In a method of forming a photonic device, a first silicon electrode is formed, and then a germanium active layer is formed on the first silicon electrode while including n-type dopant atoms in the germanium layer, during formation of the layer, to produce a background electrical dopant concentration that is greater than an intrinsic dopant concentration of germanium. A second silicon electrode is then formed on a surface of the germanium active layer. The formed germanium active layer is doped with additional dopant for supporting an electrically-pumped guided mode as a laser gain medium with an electrically-activated n-type electrical dopant concentration that is greater than the background dopant concentration to overcome electrical losses of the photonic device.

High-concentration active doping in semiconductors and semiconductor devices produced by such doping

A chip-scale, air-clad semiconductor pedestal waveguide can be used as a mid-infrared (mid-IR) sensor capable of in situ monitoring of organic solvents and other analytes. The sensor uses evanescent coupling from a silicon or germanium waveguide, which is highly transparent in the mid-IR portion of the electromagnetic spectrum, to probe the absorption spectrum of fluid surrounding the waveguide. Launching a mid-IR beam into the waveguide exposed to a particular analyte causes attenuation of the evanescent wave's spectral components due to absorption by carbon, oxygen, hydrogen, and/or nitrogen bonds in the surrounding fluid. Detecting these changes at the waveguide's output provides an indication of the type and concentration of one or more compounds in the surrounding fluid. If desired, the sensor may be integrated onto a silicon substrate with a mid-IR light source and a mid-IR detector to form a chip-based spectrometer.

Methods and apparatus for mid-infrared sensing

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Stoughton, MA, United States of America

Yan Cai