Influence of internal electric fields and surface charges on the transport of an optically generated electron-hole plasma

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Abstract
A hydrodynamic description based on a heated displaced Maxwellian approximation is used to investigate the perpendicular transport of an electron-hole plasma, generated by a laser pulse in a thin semiconductor slab. Internal electric fields and surface charges are built up due to different bulk and surface properties of the two charge-carrier types. The response of the plasma is studied on different time and length scales in terms of hydrodynamic and electric variables. If the surface charges are small, the internal electric field is measurable as a small external voltage known as the Dember effect. In this regime, the field has practically no influence on the transport, and an ambipolar model can be applied for the calculation of the hydrodynamic variables. Large surface charges, however, lead to fields much stronger than the Dember field and limit the validity of the ambipolar approximation.