1212.0930 (D. J. Carrad et al.)

(NH4)2Sx passivation of the (311)A GaAs surface in AlGaAs/GaAs
heterostructures    [PDF]

D. J. Carrad, A. M. Burke, P. J. Reece, R. W. Lyttleton, D. E. J. Waddington, A. Rai, D. Reuter, A. D. Wieck, A. P. Micolich

We have studied the efficacy of (NH4)2Sx surface passivation on the (311)A GaAs surface, and in particular, as a possible solution to the gate hysteresis problem in transistors made using Si-doped p-type (311)A AlGaAs/GaAs heterostructures. We report XPS studies of simultaneously-grown (311)A and (100) heterostructures showing that the (NH4)2Sx solution removes the surface oxide and sulfidizes both surfaces. Passivation is typically characterized using photoluminescence measurements, and we show that while (NH4)2Sx treatment gives a 40-60 times increase in photoluminescence intensity for the (100) surface, an increase of only 2-3 times is obtained for the (311)A surface. A corresponding lack of reproducible improvement in the gate hysteresis of (311)A heterostructure transistor devices made with the passivation treatment performed immediately prior to gate deposition is also found. We discuss possible reasons for why sulfur passivation is ineffective on the (311)A GaAs surface, and propose several alternative strategies for passivation of this surface.

View original: http://arxiv.org/abs/1212.0930