Evaluation of deep levels in In_0.53Ga_0.47As and GaAs_0.5Sb_0.5 using low‐frequency noise and RTS noise characterization

Abstract

Quantum‐well photodetectors based on lattice‐matched InGaAs/GaAsSb heterostructures on InP are promising candidates for mid‐infrared detection. However, the dark current in these devices can be elevated by the presence of deep levels. In this work, both bulk and interfacial deep levels in MBE‐grown homojunctions and heterojunctions are studied experimentally using low‐frequency noise spectroscopy and random telegraph signal (RTS) characterization. Several bulk and interface‐related levels have been identified and characterized in terms of energy level, cross‐section and trap type. It is expected that these ongoing defect studies will enable the growth of the higher‐quality material and heterostructures needed for future‐generation mid‐IR detectors and devices. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigation of a near mid-gap trap energy level in mid-wavelength infrared InAs/GaSb type-II superlattices

“…Indeed, consistent results from LFNS and DLTS were reported [44,45]. Unfortunately, despite its many advantages, LFNS without additional random telegraph signal analysis does not allow direct information about the trap type (if it is donor-or acceptor-like) to be obtained [41,46]. Moreover, there are some difficulties in making a direct connection between E a av and the relative trapping state energy value, E t , owing to the usually-unknown thermal dependence of f 0 .…”

Investigation of traps in strained‐well InGaAs/GaAsSb quantum well photodiodes

“…Defects in this device structure were evaluated using both DLTS and LFNS. For the LFNS study, the frequency‐weighted noise spectra were taken to be expressed as [7, 10] where the three contributions to the measured noise spectra correspond to Lorentzians of generation‐recombination (G‐R) noise with carrier lifetimes of τ 0 i , 1/ f noise, and white noise, respectively. Devices with areas of 4.91 × 10 −4 cm 2 were measured over a temperature range from 100 to 300 K as a function of forward current density.…”

“…For E 2 , traps with similar energy and cross‐section have been observed in lattice‐matched QW structures [7]. Since LFNS is not able to resolve the ‘type’ (either hole or electron) of a trap, this defect could either be a donor‐like level in InGaAs with energy 0.13 eV below the conduction band edge (after compensating for an electron ground state energy of 0.12 eV) and cross‐section of 1.14 × 10 −16 cm 2 , or an acceptor‐like level in GaAsSb with energy 0.20–0.22 eV above the valence band edge and cross‐section of 1.08 × 10 −17 cm 2 .…”

“…However, absorption alone is insufficient to yield highperformance photodetectors, and noise must also be considered. It has been shown that the noise performance of the conventional structure is limited by excess dark current due to the existence of deep levels in the active region [4][5][6][7]. One might expect that the more complex strained-well QW structure could exhibit similar limitations as well, but this has not been previously studied.…”

“…Results and discussion: Defects in this device structure were evaluated using both DLTS and LFNS. For the LFNS study, the frequencyweighted noise spectra were taken to be expressed as [7,10] 2pf…”