Measurement of Minority Charge Carrier Diffusion Length in Gallium Nitride Nanowires Using Electron Beam Induced Current (EBIC)

摘要

Electron Beam Induced Current (EBIC) measurements were performed on GaN nanowires to determine minority charge carrier diffusion length, Ld. Although EBIC has been used to characterize bulk and thin film materials, very little is known about near contact transport in GaN nanowires. The results obtained from EBIC will be compared against those obtained from a novel Nearfield Scanning Optical Microscopy (NSOM) method developed at the Naval Postgraduate School (NPS) that provides an alternative method for the determination of Ld. Two types of nanowires were investigated: n-type GaN/AlGaN (core-shell) nanowires and unintentionally doped (UID) n-type GaN uncoated nanowires. By exciting the nanowires using an electron beam in the SEM, the EBIC signal collected at the metal-semiconductor Schottky contact represents a diffusive current. Diffusion length can then be extracted from the spatial variation of the EBIC signal. The diffusion length of holes in the GaN/AlGaN wires was measured to be 1.2 micron +/- 22% and the diffusion length of holes in the UID GaN uncoated wires was measured to be 0.40 micron +/- 24%. The results demonstrate the dependence of diffusion length on the diameter and surface behavior of the nanowire.