Silicon-based photodiodes for enhanced infrared detection, quick response and low cost
The technology offered here is for the creation of an “impurity enhanced” silicon material with unique optelectric properties. The material is created by employing an ion-implantation technique using a nanosecond laser to melt the basis of single silicon crystal. Sulfur and selenium are then ion-implanted into silicon. The implanted layer is then damaged and becomes amorphous. After that, a 1 to 50ns laser pulse is employed to melt the material to a depth slightly greater than the thickness of the amorphous layer. The melted material then solidifies as a single crystal of quality comparable to a virgin silicon wafer. Annealing is also required for some samples. This photodiode displays significant response out to a wavelength of 1350nm while ordinary silicon has difficulty over 1000nm.
Intellectual Property Status: Patent(s) Pending
Silicon photodiodes are widely used in biological and medical imaging applications. They have low dark noise, high response speeds and relatively low cost. The conventional silicon photodiode works very well in the 700-900nm wavelength region with high efficiency and response times. However, because of the intrinsic limitations of the material, silicon produces a huge drop in sensitivity above 1000nm. Additionally, alternatives to silicon-based photo diodes such as InGaAs are expensive and difficult to use.
A team of Harvard physicists led by Michael J. Aziz has developed a new type of silicon photodiode which has much higher sensitivity at the IR wavelength when compared to conventional silicon photodiodes. This technology brings new opportunities for imaging techniques, manufacturing industries and telecommunications.