Title :
Negative photoresponse in modulation doped field effect transistors (MODFET´s): theory and experiment
Author :
Romero, Murilo A. ; Herczfeld, Peter R.
Author_Institution :
Center for Microwave/Lightwave Eng., Drexel Univ., Philadelphia, PA, USA
fDate :
3/1/1995 12:00:00 AM
Abstract :
A model for the mechanism of negative photoresponse, namely, the decrease of drain current under illumination, in AlGaAs-GaAs MODFET´s is presented. Also, a comprehensive experimental study discussing the dependence of this phenomena on gate and drain to source bias voltages and optical power, as well as a comparison with devices that show the usual positive photoresponse, are reported. The negative photoresponse is attributed to trapping of photogenerated carriers in the GaAs buffer layer, causing a change in the potential profile and consequent reduction in the number of carriers in the 2-DEG channel. The above theory is supported by numerical solution of Poisson´s and electron continuity equation, using the finite-elements method. Finally, the implications of the negative photoresponse on the high-speed photodetection properties of MODFET´s devices are discussed
Keywords :
III-V semiconductors; aluminium compounds; electron traps; finite element analysis; gallium arsenide; high electron mobility transistors; photoconductivity; photodetectors; phototransistors; semiconductor device models; two-dimensional electron gas; 2DEG channel; AlGaAs-GaAs; FEM; GaAs buffer layer; MODFET; Poisson equation; bias voltages; drain current; electron continuity equation; field effect transistors; finite-elements method; high-speed photodetection properties; model; modulation doped FET; negative photoresponse; optical control device; optical power; photogenerated carrier trapping; Epitaxial layers; FETs; HEMTs; High speed optical techniques; Lighting; MODFETs; Optical buffering; Optical devices; Optical modulation; Voltage;
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
