Design of an optical response system for characterization of hyperoped silicon photodetectors

Silicon photonics requires the realization of CMOS-compatible infrared detectors for large scale integration. One possible solution for infrared detection in Si is through the use of hyperdoping, where supersaturated solutions of impurities in Si are produced in order to create intermediate bands in between the valence and conduction bands in Si. Sub-band gap photoconductivity was recently demonstrated in a prototype photodetector fabricated from Si hyperdoped with Au, with infrared response at wavelengths as long as 2 æm. The thesis focuses on the design and fabrication of an optical and electrical measurement system for the characterization of prototype photodiode detectors fabricated from Au-hyperdoped material in order to further its development. Measurement of detector response at long wavelengths requires design of an optical system that can deliver long wavelength light to the device and an electrical system that can measure the (possibly small) photocurrent induced in the detector. An optical system was designed and implemented using a purpose-built tungsten halogen lamp and monochromator as the illumination source, with a custom infrared lensed fiber to deliver the light. In order to characterize on-chip devices, a micro-probe station was employed for electrical connectivity. The system measures electrical response by modulating the incident light with an optical chopper and measuring the change in voltage across a series resistor using a lock-in amplifier as the wavelength is changed. The intensity output of the optical system was measured using calibrated photodiodes covering the wavelength range 800-2600 nm. The system showed measureable light over the entire wavelength range. To couple the max amount of IR to the detector, a large NA and core size silica fiber and a small filament, high power light source are considering to substitute into the system. And the ultimately illumination power can be increased by 25 times. This demonstrates that this system can be used to characterize detectors fabricated from Au-hyperdoped Si