Measurement of piezoelectrically induced charge in GaN/AlGaN heterostructure field-effect transistors

Abstract

Electron concentration profiles have been obtained for Al x Ga 1Ϫx N/GaN heterostructure field-effect transistor structures. Analysis of the measured electron distributions demonstrates the influence of piezoelectric effects in coherently strained layers on III-V nitride heterostructure device characteristics. Characterization of a nominally undoped Al 0.15 Ga 0.85 N/GaN transistor structure reveals the presence of a high sheet carrier density in the GaN channel which may be explained as a consequence of piezoelectrically induced charges present at the Al 0.15 Ga 0.85 N/GaN interface. Measurements performed on an Al 0.15 Ga 0.85 N/GaN transistor structure with a buried Al 0.15 Ga 0.85 N isolation layer indicate a reduction in electron sheet concentration in the transistor channel and accumulation of carriers below the Al 0.15 Ga 0.85 N isolation layer, both of which are attributable to piezoelectric effects.

Highly efficient photochemical HCOOH production from CO2 and water using an inorganic system

“…The uid-AlGaN has a role in the efficient conversion from photons to electron-hole pairs that trigger chemical reactions. 18,19 Such a heterostructure is expected to have an electric polarization in the uid-AlGaN layer, [20][21][22][23][24] which makes electron-hole separation more effective. The thin films were grown by atmospheric-pressure metal organic vapor-phase epitaxy (MOVPE) on (0001) sapphire substrate with low-temperature GaN buffer layer.…”

Pyroelectric and Piezoelectric Properties of GaN-Based Materials

“…The surface charge density induced by the piezoelectric effect in AlGaN-GaN Heterostructure Field-Effect Transistors (HFETs) can be on the order of 10 12 -10 13 cm -2 . 8,26,27 These results are very important for developing of a new class high power, high temperature electron devices, such as microwave power amplifiers and power switches.…”

“…Electron sheet concentrations as high as 3x10 13 cm -2 or more can be induced by the piezoelectric effect. 8,26,27 The elastic strain relaxation and the piezoelectric doping in Al x Ga 1-x N-GaN HFETs were studied in References 24,12 . We calculated the Al x Ga 1-x N/GaN band structure by solving Poisson's equation with the boundary conditions for the Al x Ga 1-x N /GaN interface, which account for the piezoelectric effect:…”

Dipole scattering in polarization induced III–V nitride two-dimensional electron gases

“…In fact the spontaneous and piezoelectric polarization is large enough to produce 2DEGs without intentionally doping the barrier, leading to the novel concept of piezoelectric doping in such systems [Ref. 9,10]. The term 'modulation doped hetersostructures' (MDHs) is somewhat erroneous in such devices, so we prefer to call it the more general HEMTs.…”