The Mobility Requires a Separation
The Mobility Requires a Separation
An ordinary semiconductor pins its dopant atoms in the same crystal plane as the electrons they donate. HEMT abandons this. It stacks two dissimilar semiconductors and confines electrons to a channel physically apart from the ionized donors that gave them up. Coulomb scattering, the drag of charge against its own broken-off parent, disappears.
Freed of their source, electrons in the channel move as if the crystal were flawless — mobility rising by an order of magnitude, noise falling until faint microwave whispers survive amplification intact.
Seed: High-electron-mobility transistor (HEMT) / modulation doping.
Central fact: A HEMT separates donor impurities from the conduction channel so electrons flow without impurity scattering, achieving ultra-high mobility and the low-noise amplification cryogenic quantum readout depends on.
