Resonant-Tunnelling Hot Electron Transistors (RHET)

Abstract

Heiblum proposed a hot electron transistor, THETA, that [8.1] used semiconductor heterojunctions. The good lattice match and the single-crystal epitaxial growth with molecular beam epitaxy (MBE) provides superior interfaces difficult to obtain with metal-oxide or metal-semiconductors. The very short carrier transit time indicates the potential application for very high speed devices. We fabricated hot electron transistors using [8.2, 3] MBE-grown GaAs/AlGaAs heterostructures. The device had a current gain of more than one at 40 K. We were the first to propose hot electron spectroscopy using the hot electron transistor [8.3], and measured the hot electron spectrum. However, we could not observe ballistic transport in this device due to scattering into the upper satellite valley in the AlGaAs collector barrier. We noticed evidence of near-ballistic transport in the base region of this device by measuring the transfer ratio of the hot electron transistor in a magnetic field [8.4]. We found that the transfer ratio decreases as the magnitude of the magnetic field normal to the direction of injection increases. We attribute this to the cyclotron motion of hot electrons. From these observations, the transit time for a 100 nm GaAs base was estimated to range from 0.1 ps to 1.0 ps [8.5], indicating a transit velocity from 1 × 10⁷ to 1 × 10⁸ cm/s suggesting near-ballistic transport in the base region.