Probing and modelling the localized self-mixing in a GaN/AlGaN   field-effect terahertz detector
  In a GaN/AlGaN field-effect terahertz detector, the directional photocurrent is mapped in the two-dimensional space of the gate voltage and the drain/source bias. It is found that not only the magnitude, but also the polarity, of the photocurrent can be tuned. A quasistatic self-mixing model taking into account the localized terahertz field provides a quantitative description of the detector characteristics. Strongly localized self-mixing is confirmed. It is therefore important to engineer the spatial distribution of the terahertz field and its coupling to the field-effect channel on the sub-micron scale. 
J. D. Sun, H. Qin, R. A. Lewis, Y. F. Sun, X. Y. Zhang, Y. Cai, D. M.   Wu, and B. S. Zhang
cond-mat.mes-hall physics.optics