Study of dynamic behavior of δ-doped HMSM photodetector

We have previously reported the time response of a δ-doped heterostructure metal-semiconductor-metal photodetector (HMSM-PD) with FWHM of 11 ps for a 4 μm finger gap device. Comparison of the δ-doped and undoped devices shows improved performance due to the δ-doping. In this paper, we simulate the device dynamics behavior using Ramo´s theorem. Results show that the introduction of a δ-doping layer significantly changes the 2D potential and field profiles from horizontally oriented to vertically oriented ones due to the screening effect of the highly crowded two dimensional electron gas (2DEG) formed along the interface of the heterojunction, which reduces the carrier travel distance, hence the transit time of carriers in the device. With this knowledge, we expect to achieve high speed performance without further scaling down of the device.