Time Response of Two-Dimensional Gas-Based Vertical Field Metal–Semiconductor–Metal Photodetectors

We have fabricated and characterized 2-D gas-based, including 2-D electron gas (2DEG) and 2-D hole gas (2DHG), heterostructure metal-semiconductor-metal (MSM) photodetectors on GaAs. Both the high-speed measurement of time response and the simulation results show that a vertical field developed in the active absorption region due to the delta-doping layer facilitates one type of photogenerated carrier transport. In addition, the confined carriers facilitate collection of the optically generated carriers that reach them. The vertical field in the MSM structure that is created by a 2-D gas transforms a traditional lateral MSM device to a vertical one, although remaining as a planar structure, thus allowing a device design for high-speed performance without sacrificing the external quantum efficiency.