Heterostructures in MODFETs

Physics-based compact modeling of quasi-ballistic transistors

“…carriers in an undoped region, thus, reducing the impurity scattering. The doped regions act as supplier of carriers [7]. The spatial separation between the doped and undoped regions is achieved with the heterostructure band alignment that results in a low energy notch or potential well, as shown in Several improvements have been made to the HEMT structure to enhance its performance [7].…”

“…The doped regions act as supplier of carriers [7]. The spatial separation between the doped and undoped regions is achieved with the heterostructure band alignment that results in a low energy notch or potential well, as shown in Several improvements have been made to the HEMT structure to enhance its performance [7]. Nitride based HEMTs (GaN), owing to the built-in polarization field, do not need a doping region to have localized carriers.…”

“…The triangular potential notch is more like a triangular quantum well with quantized subbands whose effect is significant in III-V devices. This is because, unlike silicon based devices, the Fermi level lies deep within the triangular well resulting in significant quantum mechanical effects [7]. Because of these pronounced quantum mechanical effects, φ s -based models, as discussed in previous section, cannot be used to accurately capture the physics of devices even though they can be used for mere fitting of the measurement data.…”

“…To further improve the carrier confinement and mobility, rectangular QW based structures have been introduced [12], [13]. Such devices, unlike the single heterojunction HEMTs, use a rectangular quantum well for confining electrons [7]. AlGaAs/GaAs/AlGaAs based double heterostructures are examples of such devices [7].…”

“…Such devices, unlike the single heterojunction HEMTs, use a rectangular quantum well for confining electrons [7]. AlGaAs/GaAs/AlGaAs based double heterostructures are examples of such devices [7]. The schematic and conduction band profile of a double hetrostucture HEMT is shown in Fig.…”