Most people with diabetes suffer some deterioration of the feet. Diabetic foot syndrome causes ulceration in about 15% of cases and such deterioration leads to amputation in about 2.5% of diabetic patients, diminishing their quality of life and generating extraordinary costs for patients and public health systems. Currently, there is no objective method for the detection of diabetic foot syndrome in its early stages. We propose terahertz imaging as a method for the evaluation of such deterioration. This screening method could aid the prevention and medical treatment of this condition in the future.

We use a Monte-Carlo model to simulate semi-classical photo-carrier dynamics of InAs, InGaAs, and GaAs that leads to terahertz emission. We compare the emission power of all three semiconductors as a function of excitation photon energy finding that the carrier excess excitation energy is more relevant to explain their performance difference than their mobilities. We conclude that ballistic transport after photoexcitation is the dominant mechanism for terahertz emission instead of diffusion driven or surface field driven charge separation, which were traditionally considered the most relevant mechanisms.

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