Influence of surface passivation on ultrafast carrier dynamics and terahertz radiation gene.pdf

PREPRINT: To appear in Appl. Phys. Lett. 89, (Nov 2006) Influence of surface passivation on ultrafast carrier dynamics and terahertz radiation generation in GaAs J. Lloyd-Hughes∗ and S.K.E. Merchant 6 University of Oxford, Department of Physics, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, United Kingdom 0 0 L. Fu, H.H. Tan, and C. Jagadish 2 Department of Electronic Materials Engineering, Research School of Physical Sciences and Engineering, t Institute of Advanced Studies, Australian National University, Canberra ACT 0200, Australia c O E. Castro-Camus and M.B. Johnston† 0 University of Oxford, Department of Physics, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, United Kingdom 2 (Dated: 4th October 2006 (submission)) The carrier dynamics of photoexcited electrons in the vicinity of the surface of (NH ) S-passivated ] 4 2 i GaAs were studied via terahertz (THz) emission spectroscopy and optical-pump THz-probe spec- c s troscopy. THz emission spectroscopy measurements, coupled with Monte Carlo simulations of THz - emission, revealed that the surface electric field of GaAs reverses after passivation. The conductivity l r of photoexcited electrons was determined via optical-pump THz-probe spectroscopy, and was found t to double after passivation. These exper