Gate metal induced reduction of surface donor states of AlGaN/GaN heterostructure on Si-substrate investigated by electroreflectance spectroscopy

The surface donor state of AlGaN/GaN heterostructure on Si-substrate was investigated at the presence of Schottky gate metal (Au,Ni) on the surface by using electroreflectance spectroscopy. The sheet carrier density of two-dimensional electron gas (2DEG) decreased significantly from 1.03 x 10(13)cm(-2) to 5.74 x 10(12)cm(-2) for Au and from 1.03 x 10(13)cm(-2) to 3.68 x 10(12)cm(-2) for Ni upon the introduction of Schottky gate metal. Through the analysis of the depletion of 2DEG, which is attributed to both Schottky junction and the lowered energy of Schottky barrier height, it was concluded that the diminished sheet carrier density of 2DEG originated from the reduction of surface donor state induced by gate metal. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695056]