Study of RTS noise and excess currents in lattice-mismatched InP/InGaAs/InP photodetector arrays

Abstract

Random telegraph signal (RTS) or burst noise and excess current have been investigated in arrays of infrared photodetectors ( λ = 1.7 μm) prepared on lattice-mismatched InP/InGaAs/InP hetero-structures. RTS noise is observed in about 1% of devices of the wafer. At reverse bias RTS is always related to distinct excess currents (EC) which in certain cases exhibit a tunnelling behavior. Burst noise at forward biases is not necessarily correlated with the observation of distinguishable excess currents. RTS amplitudes and excess currents are thermally activated. At reverse bias their activation energies are in the 0.15–0.35 eV range. The pulse width distribution of a two level RTS is obtained by using an original digital data processing method. RTS mean pulse width strongly varies with temperature (activation energies in the 0.22–1.30 eV range) and also depends on applied bias. The results suggest that RTS noise is due to excess current which flows through a crystalline defect and is modulated by an action of a small lattice defect. Two alternative RTS models are discussed to explain the data. Finally the influence of substrate dislocations and lattice-mismatched defects on the presence of excess noise is discussed.