ELECTRICAL CHARACTERISTICS OF CORE-SHELL p-n GaAs NANOWIRE STRUCTURES WITH Te AS THE n-DOPANT

JORGE CARAM; CLAUDIA SANDOVAL; M. TIRADO; D. COMEDI; JOSEF CZABAN; R. R. LAPIERRE

Hamilton, Ontario

Congreso; 14th Canadian Semiconductor Technology Conference and Nano and Giga Challenges in Electronics, Photonics and Renewable Energy; 2009

McMaster University

The current status of nanowire (NW) photovoltaic (PV) devices is far from satisfactory as laboratory efficiencies are still much lower than the theoretical limits. Here we examine, by impedance spectroscopy at various frequencies and DC biases, GaAs NW-based p-n junction PV-devices where Te was used as the n-dopant to overcome the amphoteric behavior of Si in GaAs NWs. Two samples exhibiting two distinct p and n spatial distributions and sizes were studied. For a large n core/p shell overlap region within NWs in a coaxial geometry, the p-n junction properties (DC rectification and p-n depletion capacitance) are found to prevail. The impedance data for both NW devices show large frequency dispersions with relaxation frequencies that are compatible with carrier reemission times from traps due to GaAs surface states. An increasing conductance with increasing frequency is observed, which we interpret as an evidence for the predominance of surface hopping over multiple trapping transport, as expected from the large NW surface area to volume ratio and nearly full NW p-n junction depletion conditions.