High-speed photodiodes for the mid-infrared spectral region 1.2-2.4 μm based on GaSb/GaInAsSb/GaAlAsSb heterostructures with a transmission band of 2-5 GHz

High-speed p-i-n photodiodes for the spectral range of 1.2-2.4 mu m are fabricated for the first time based on a GaAs/GaInAsSb/GaAlAsSb heterostructure with separated sensitive-(50 mu m in diameter) and contact mesas, which are connected by a bridge front contact. The use of an unconventional design for the contact mesa with a Si3N4 insulating sublayer 0.3 mu m thick under the metal contact made it possible to lower both the intrinsic photodiode capacitance and the reverse dark currents. The photodiodes have a low intrinsic capacitance of 3-5 pF at zero bias and 0.8-1.5 pF at a reverse bias of 3.0 V. The photodiode operating speed, which is determined by the time of increasing the photoresponse pulse to a level of 0.1-0.9, is 50-100 ps. The transmission band of the photodiodes reaches 2-5 GHz. The photodiodes are characterized by low reverse dark currents I (d) = 200-1500 nA with a reverse bias of U = -(0.5-3.0) V, a high current monochromatic sensitivity of R (i) = 1.10-1.15 A/W, and a detectability of D*(lambda(max), 1000, 1) = 0.9 x 10(11) W-1 cm Hz(1/2) at wavelengths of 2.0-2.2 mu m.