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 µm are fabricated for the first time based on a GaAs/GalnAsSb/GaAlAsSb heterostructure with separated sensitive- (50 µm 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 [Si.sub.3][N.sub.4] insulating sublayer 0.3 µm 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.sub.d] = 200-1500 nA with a reverse bias of U = -(0.5-3.0) V, a high current monochromatic sensitivity of [R.sub.i] = 1.10-1.15 A/W and a detectability of [D.sup.*] ([λ.sub.max], 1000, 1) = 0.9 x [10.sup.11] [W.sup.-1] cm [Hz.sup.1/2] at wavelengths of 2.0-2.2 µm. DOI: 10.1134/S1063782613080046