Influence of Contacts and Applied Voltage on a Structure of a Single GaN Nanowire

Semiconductor nanowires (NWs) have a broad range of applications for nano- and optoelectronics. The strain field of gallium nitride (GaN) NWs could be significantly changed when contacts are applied to them to form a final device, especially considering the piezoelectric properties of GaN. Investigation of influence of the metallic contacts on the structure of the NWs is of high importance for their applications in real devices. We have studied a series of different type of contacts and influence of the applied voltage bias on the contacted GaN NWs with the length of about 3 to 4 micrometers and with two different diameters of 200 nm and 350 nm. It was demonstrated that the NWs with the diameter of 200 nm are bend already by the interaction with the substrate. For all GaN NWs, significant structural changes were revealed after the contacts deposition. The results of our research may contribute to the future optoelectronic applications of the GaN nanowires.

Electronic performance of GaN nanowires cathode under electric field

The built-in electric field of exponential doping can promote the concentration of the photogenerated carrier center to the top surface of the nanowire. The external electric field also can bend the motion trajectory of the emitted electrons toward the collecting side. These field-assisted methods promote the quantum efficiency. In this paper, the emission theory of a single GaN nanowire photocathode is studied for the first time. The effects of height and width of the nanowire, wavelength, intensity of electric field on quantum efficiency of uniformly doped or exponentially doped GaN nanowire photocathodes were explored. It shows that the top of the exponentially doped cathode has a higher quantum efficiency than uniformly doped cathode. With the absence of the field, quantum efficiency of a uniformly doped cathode reaches a maximum value of 55.29% when the width is 150 nm and the wavelength is 220 nm. The form of exponentially doped cathode can generate an internal field. With the internal field, a maximum value rises 56.73% when the height is 900 nm and the wavelength is 230 nm. The theoretical results can direct the preparation of this kind of photocathode.