Size-dependent persistent photocurrent and surface band bending in m-axial GaN nanowires
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
84
Journal Issue
20
Date Issued
2011
Author(s)
Abstract
The size-dependent persistent photocurrent (PPC), which refers to a photocurrent persisting for a long time after the excitation light source is terminated, has been investigated in m-axial GaN nanowires (NWs) with diameters of 20-130 nm. These NWs possess polar side surfaces and thus exhibit strong surface band bending (SBB). With different diameters, a different rise time in photoconductivity (PC) upon excitation light illumination and a different decay time in the PPC are observed; the latter is attributed to a long carrier lifetime caused by a frustrated recombination process. The intensity (I)-dependent photocurrent-gain (Γ) measurement displays a Γ-I dependence that follows a power-law relationship with fitting indices of ∼0.85-0.89, indicating that the long carrier lifetime-induced PPC of GaN NWs is caused by an SBB effect instead of a bulk trap effect. In addition, size-dependent decay times reveal two regimes for the different sizes of NWs. The decay time of the NW above critical diameter (dcrt, 30-40 nm) is found to be ∼13 000 s, while the smaller NW (
Publisher
American Physical Society
Type
journal article