65-GHz Bandwidth 900-1600 nm Photodetector

The objective of this Phase I is to develop a novel 65-GHz bandwidth photodetector with high sensitivity between 900-1600 nm. This detector will have a response time of 5 ps, making it the fastest near-IR photodetector available. It will have a responsivity of 0.2 A/W and dark current < 50 nA, with an active area of 50x50 square micrometers. It will also be capable of generating signals with amplitudes exceeding 1 volt into 50 ohms. This detector will function like a photoconductor instead of a photodiode. Its speed will be derived from deep-level traps that form in InGaAs when grown under non-stoichiometric molecular-beam-epitaxy conditions. This technique has been applied by us to non-stoichiometric growth of GaAs to yield a 400-900 nm, metal-semiconductor-metal detector with 0.1 A/W sensitivity and 1 ps response time. This is the fastest visible photodetector in the world. During this Phase I we will develop the non-stoichiometric growth conditions for InGaAs. We will also use a newly developed 2-picosecond-resolution electrical probe to help design the ideal electrode geometries for both the detector and microwave launcher.