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Abstract
We report on positive and negative persistent photo-effects observed in some red light emitting diode (LED)-illuminated type-II InAs/GaSb superlattices (SLs) grown on a p-type GaSb. By analyzing the time dependence of the transverse resistance during and after the illumination, we show that the rise and decay curves are logarithmic, a behavior which points to hierarchically constrained carrier dynamics. Accordingly, negative persistent effects are explained by diffusion and trapping of photo-excited carriers in the p-type buffer layer and their subsequent tunneling back to the SL. On the other hand, positive persistent effects are explained by a low density of majority-carrier trapping centers in the buffer layer. Hence, persistent photo-effects upon red-LED irradiation provide a diagnostic of the quality of the superlattice-buffer interface.
Highlights
There is interest in improving the material properties of type-II InAs/GaSb superlattices (SLs) because of their important applications as infrared detectors and lasers.1–10 While experimenting with various growth parameters, we found that some samples grown under special conditions exhibited persistent photo-effects upon illumination with a red-light emitting diode (LED).11 We exploited the resulting variability in carrier density and carrier type to study the in-plane carrier mobility in InAs/GaSb SLs as a function of carrier density.11 The study of the possible sources of these persistent effects is the subject of the present paper.Persistent photoconductivity (PPC) has been observed in many III–V and II–VI semiconductors14–16 and has been often ascribed to various defects
We report on positive and negative persistent photo-effects observed in some red light emitting diode (LED)-illuminated type-II InAs/GaSb superlattices (SLs) grown on a p-type GaSb
By analyzing the time dependence of the transverse resistance during and after the illumination, we show that the rise and decay curves are logarithmic, a behavior which points to hierarchically constrained carrier dynamics
Summary
There is interest in improving the material properties of type-II InAs/GaSb superlattices (SLs) because of their important applications as infrared detectors and lasers. While experimenting with various growth parameters, we found that some samples grown under special conditions exhibited persistent photo-effects upon illumination with a red-light emitting diode (LED). We exploited the resulting variability in carrier density and carrier type to study the in-plane carrier mobility in InAs/GaSb SLs as a function of carrier density. The study of the possible sources of these persistent effects is the subject of the present paper. The long relaxation times were explained by a slow movement of electrons from the InAs quantum well to the ionized deep levels in the AlSb barriers They ruled out interface states or fluctuations of the potential at the InAs QW interfaces, arguing that25 “a random distribution of energies is typical for defect states at interfaces, and should not give rise to a relaxation process with a single time constant.”. We study persistent photo-effects in type-II InAs/GaSb superlattices grown on p-type GaSb substrates by measuring the in-plane resistance during and after illumination with a red LED. We show that the decay and rise curves depend logarithmically on time, which suggests hierarchically constrained dynamics invoked earlier by Quisser but in connection with a positive persistent photoeffect in n-type layers on semi-insulating substrates.
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