60 research outputs found
Infrared conductivity of hole accumulation and depletion layers in (Ga,Mn)As- and (Ga,Be)As-based electric field-effect devices
We have fabricated electric double-layer field-effect devices to
electrostatically dope our active materials, either =0.015
GaMnAs or =3.2 GaBeAs. The devices
are tailored for interrogation of electric field induced changes to the
frequency dependent conductivity in the accumulation or depletions layers of
the active material via infrared (IR) spectroscopy. The spectra of the
(Ga,Be)As-based device reveal electric field induced changes to the IR
conductivity consistent with an enhancement or reduction of the Drude response
in the accumulation and depletion polarities, respectively. The spectroscopic
features of this device are all indicative of metallic conduction within the
GaAs host valence band (VB). For the (Ga,Mn)As-based device, the spectra show
enhancement of the far-IR itinerant carrier response and broad mid-IR resonance
upon hole accumulation, with a decrease of these features in the depletion
polarity. These later spectral features demonstrate that conduction in
ferromagnetic (FM) GaMnAs is distinct from genuine metallic
behavior due to extended states in the host VB. Furthermore, these data support
the notion that a Mn-induced impurity band plays a vital role in the electron
dynamics of FM GaMnAs. We add, a sum-rule analysis of the spectra
of our devices suggests that the Mn or Be doping does not lead to a substantial
renormalization of the GaAs host VB
PN junction rectification in electrolyte gated Mg-doped InN
PN junction rectification is demonstrated in indium nitride. The junction is formed between the n-type surface accumulation layer and the Mg-doped, p-type bulk in a top-contacted thin film structure. The parasitic shorting path between the top contacts is controlled by gating with an electrolyte. For positive gate voltages, electrons accumulate at the surface and the current flows preferentially through n type regions, and linear current-voltage (I-V) behavior is observed. However, for negative gate voltages, surface electrons are depleted and current flows through the p-type bulk. This creates an n-p-n structure and a characteristic non-linear I-V curve is observed. [doi:10.1063/1.3634049
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