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The region for the n- and p-GaN samples without and under illumination with a 50 mW 405 nm laser. The experimental set-up is shown as an inset.
(a) The B.E. changes recorded in the transient mode with 0.1 s intervals, as the laser is turned ON and OFF at 0.01 Hz frequency, with the flood-gun turned-off (red, upper) and turned-on (cyan, lower). (b) Exponential fits to the laser ON and OFF time-windows for the p-GaN with flood-gun electrons.
Mechanisms involved in n-GaN (a) and p-GaN (b) with illumination. SPV is generated by excitation of electrons or holes out of surface states by subbandgap illumination at a rate of . SPV decays under dark conditions by thermal excitation of electrons or holes over the surface barrier at a rate of . Flood-gun electrons (indicated by blue dots) are swept to the bulk for n-GaN, and to the surface for p-GaN.
(a) The same data as presented in Fig. 2(a) for the p-GaN. (b) The B.E. changes recorded in the transient mode with 0.1 s intervals, as the sample is subjected to SQW electrical pulses with 10 V amplitude and 0.01 Hz frequency and with the flood-gun turned-on. The inset shows the expanded version of the data.
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